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52 rational expressions

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Rational Expressions Frank Ma © 2011
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Page 1: 52 rational expressions

Rational Expressions

Frank Ma © 2011

Page 2: 52 rational expressions

Rational ExpressionsPolynomials are expressions of the form anxn + an-1xn-1+ an-2xn-2+…+ a1x1+ a0 where the a’s are numbers.

Page 3: 52 rational expressions

Rational Expressions

For example, 7x12 – 4x5 + 6x2 – 5,

Polynomials are expressions of the form anxn + an-1xn-1+ an-2xn-2+…+ a1x1+ a0 where the a’s are numbers.

Page 4: 52 rational expressions

Rational Expressions

For example, 7x12 – 4x5 + 6x2 – 5, πx – 0.762 are polynomials.

Polynomials are expressions of the form anxn + an-1xn-1+ an-2xn-2+…+ a1x1+ a0 where the a’s are numbers.

Page 5: 52 rational expressions

Rational Expressions

For example, 7x12 – 4x5 + 6x2 – 5, πx – 0.762 are polynomials.

Rational (fractional) expressions are expressions of the

form , where P and Q are polynomials.PQ

Polynomials are expressions of the form anxn + an-1xn-1+ an-2xn-2+…+ a1x1+ a0 where the a’s are numbers.

Page 6: 52 rational expressions

Rational Expressions

For example, 7x12 – 4x5 + 6x2 – 5, πx – 0.762 are polynomials.

Rational (fractional) expressions are expressions of the

form , where P and Q are polynomials.PQ

Polynomials are expressions of the form anxn + an-1xn-1+ an-2xn-2+…+ a1x1+ a0 where the a’s are numbers.

All polynomials are rational expressions by viewing P as .P1

Page 7: 52 rational expressions

Rational Expressions

For example, 7x12 – 4x5 + 6x2 – 5, πx – 0.762 are polynomials.

Rational (fractional) expressions are expressions of the

form , where P and Q are polynomials.PQ

Polynomials are expressions of the form anxn + an-1xn-1+ an-2xn-2+…+ a1x1+ a0 where the a’s are numbers.

All polynomials are rational expressions by viewing P as .P1

x – 2 x2 – 2 x + 1 ,

Page 8: 52 rational expressions

Rational Expressions

For example, 7x12 – 4x5 + 6x2 – 5, πx – 0.762 are polynomials.

Rational (fractional) expressions are expressions of the

form , where P and Q are polynomials.PQ

Polynomials are expressions of the form anxn + an-1xn-1+ an-2xn-2+…+ a1x1+ a0 where the a’s are numbers.

All polynomials are rational expressions by viewing P as .P1

x – 2 x2 – 2 x + 1 ,

x(x – 2) (x + 1) (2x + 1) are rational expressions.

Page 9: 52 rational expressions

Rational Expressions

For example, 7x12 – 4x5 + 6x2 – 5, πx – 0.762 are polynomials.

Rational (fractional) expressions are expressions of the

form , where P and Q are polynomials.PQ

Polynomials are expressions of the form anxn + an-1xn-1+ an-2xn-2+…+ a1x1+ a0 where the a’s are numbers.

All polynomials are rational expressions by viewing P as .P1

x – 2 x2 – 2 x + 1 ,

x(x – 2) (x + 1) (2x + 1) are rational expressions.

x – 2 2 x + 1

is not a rational expression because the

denominator is not a polynomial.

Page 10: 52 rational expressions

Rational Expressions

For example, 7x12 – 4x5 + 6x2 – 5, πx – 0.762 are polynomials.

Rational (fractional) expressions are expressions of the

form , where P and Q are polynomials.PQ

Polynomials are expressions of the form anxn + an-1xn-1+ an-2xn-2+…+ a1x1+ a0 where the a’s are numbers.

All polynomials are rational expressions by viewing P as .P1

x – 2 x2 – 2 x + 1 ,

x(x – 2) (x + 1) (2x + 1) are rational expressions.

x – 2 2 x + 1

is not a rational expression because the

denominator is not a polynomial.Rational expressions are expressions that describe calculation procedures that involve division (of polynomials).

Page 11: 52 rational expressions

Rational ExpressionsJust as polynomials may be given in the expanded form or factored form, rational expressions may also be given in these two forms.

Page 12: 52 rational expressions

Rational ExpressionsJust as polynomials may be given in the expanded form or factored form, rational expressions may also be given in these two forms. The rational expression x2 – 4

x2 + 2x + 1 is in the expanded form.

Page 13: 52 rational expressions

Rational ExpressionsJust as polynomials may be given in the expanded form or factored form, rational expressions may also be given in these two forms. The rational expression x2 – 4

(x + 2)(x – 2) (x + 1)(x + 1) .

is in the expanded form.

In the factored form, it’s

x2 + 2x + 1

Page 14: 52 rational expressions

Rational ExpressionsJust as polynomials may be given in the expanded form or factored form, rational expressions may also be given in these two forms. The rational expression x2 – 4

x2 + 2x + 1 (x + 2)(x – 2) (x + 1)(x + 1) .

x – 2 x2 + 1 The expression is in both forms.

is in the expanded form.

In the factored form, it’s

Example A. Put the following expressions in the factored form.

a. x2 – 3x – 10 x2 – 3x

b. x2 – 3x + 10 x2 – 3

Page 15: 52 rational expressions

Rational ExpressionsJust as polynomials may be given in the expanded form or factored form, rational expressions may also be given in these two forms. The rational expression x2 – 4

x2 + 2x + 1 (x + 2)(x – 2) (x + 1)(x + 1) .

x – 2 x2 + 1 The expression is in both forms.

is in the expanded form.

Example A. Put the following expressions in the factored form.

(x – 5)(x + 2)a. x(x – 3)

x2 – 3x – 10 x2 – 3x

=

b. x2 – 3x + 10 x2 – 3

In the factored form, it’s

Page 16: 52 rational expressions

Rational ExpressionsJust as polynomials may be given in the expanded form or factored form, rational expressions may also be given in these two forms. The rational expression x2 – 4

x2 + 2x + 1 (x + 2)(x – 2) (x + 1)(x + 1) .

x – 2 x2 + 1 The expression is in both forms.

is in the expanded form.

Example A. Put the following expressions in the factored form.

(x – 5)(x + 2)a. x(x – 3)

x2 – 3x – 10 x2 – 3x

=

b. x2 – 3x + 10 x2 – 3

is in the factored form

In the factored form, it’s

Page 17: 52 rational expressions

Rational ExpressionsJust as polynomials may be given in the expanded form or factored form, rational expressions may also be given in these two forms. The rational expression x2 – 4

x2 + 2x + 1 (x + 2)(x – 2) (x + 1)(x + 1) .

x – 2 x2 + 1 The expression is in both forms.

is in the expanded form.

Example A. Put the following expressions in the factored form.

(x – 5)(x + 2)a. x(x – 3)

x2 – 3x – 10 x2 – 3x

=

b. x2 – 3x + 10 x2 – 3

is in the factored form

Note that in b. the entire (x2 – 3x + 10) or (x2 – 3) are viewed as a single factors because they can’t be factored further.

In the factored form, it’s

Page 18: 52 rational expressions

We use the factored form to 1. solve equations

Rational Expressions

Page 19: 52 rational expressions

We use the factored form to 1. solve equations 2. determine the domain of rational expressions

Rational Expressions

Page 20: 52 rational expressions

We use the factored form to 1. solve equations 2. determine the domain of rational expressions2. evaluate given inputs

Rational Expressions

Page 21: 52 rational expressions

We use the factored form to 1. solve equations 2. determine the domain of rational expressions2. evaluate given inputs3. determine of the signs of the outputs

Rational Expressions

Page 22: 52 rational expressions

We use the factored form to 1. solve equations 2. determine the domain of rational expressions2. evaluate given inputs3. determine of the signs of the outputs

Solutions of Equations

Rational Expressions

Page 23: 52 rational expressions

We use the factored form to 1. solve equations 2. determine the domain of rational expressions2. evaluate given inputs3. determine of the signs of the outputs

Solutions of Equations The solutions of the equation of the form = 0 are the zeroes of the numerator, so they are the solutions of P = 0.

Rational Expressions

PQ

Page 24: 52 rational expressions

We use the factored form to 1. solve equations 2. determine the domain of rational expressions2. evaluate given inputs3. determine of the signs of the outputs

Solutions of Equations

Example B. a. Write in the factored form and

solve the equation

The solutions of the equation of the form = 0 are the zeroes of the numerator, so they are the solutions of P = 0.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

x3 + x2 – 2xx2 + 4x + 3 = 0

PQ

Page 25: 52 rational expressions

We use the factored form to 1. solve equations 2. determine the domain of rational expressions2. evaluate given inputs3. determine of the signs of the outputs

Solutions of Equations

Example B. a. Write in the factored form and

solve the equation

The solutions of the equation of the form = 0 are the zeroes of the numerator, so they are the solutions of P = 0.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

x3 – 2x2 + 3xx2 + 4x + 3

x3 + x2 – 2xx2 + 4x + 3 = 0

Factor, we get

PQ

=

Page 26: 52 rational expressions

We use the factored form to 1. solve equations 2. determine the domain of rational expressions2. evaluate given inputs3. determine of the signs of the outputs

Solutions of Equations

Example B. a. Write in the factored form and

solve the equation

The solutions of the equation of the form = 0 are the zeroes of the numerator, so they are the solutions of P = 0.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

x3 – 2x2 + 3xx2 + 4x + 3 = x(x + 2)(x – 1)

(x + 3)(x + 1)

x3 + x2 – 2xx2 + 4x + 3 = 0

Factor, we get

PQ

Page 27: 52 rational expressions

We use the factored form to 1. solve equations 2. determine the domain of rational expressions2. evaluate given inputs3. determine of the signs of the outputs

Solutions of Equations

Example B. a. Write in the factored form and

solve the equation

The solutions of the equation of the form = 0 are the zeroes of the numerator, so they are the solutions of P = 0.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

x3 – 2x2 + 3xx2 + 4x + 3 = x(x + 2)(x – 1)

(x + 3)(x + 1)

x3 + x2 – 2xx2 + 4x + 3 = 0

Factor, we get

Hence for x3 + x2 – 2xx2 + 4x + 3 = 0, it must be that x(x + 2)(x – 1) = 0

PQ

Page 28: 52 rational expressions

We use the factored form to 1. solve equations 2. determine the domain of rational expressions2. evaluate given inputs3. determine of the signs of the outputs

Solutions of Equations

Example B. a. Write in the factored form and

solve the equation

The solutions of the equation of the form = 0 are the zeroes of the numerator, so they are the solutions of P = 0.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

x3 – 2x2 + 3xx2 + 4x + 3 = x(x + 2)(x – 1)

(x + 3)(x + 1)

x3 + x2 – 2xx2 + 4x + 3 = 0

Factor, we get

Hence for x3 + x2 – 2xx2 + 4x + 3 = 0, it must be that x(x + 2)(x – 1) = 0

or that x = 0, –2, 1.

PQ

Page 29: 52 rational expressions

DomainThe domain of a formula is the set of all the numbers that we may use as input values for x.

Rational Expressions

Page 30: 52 rational expressions

DomainThe domain of a formula is the set of all the numbers that we may use as input values for x. Because the denominator of a fraction can’t be 0, therefore for the rational formulas the zeroes of the denominator Q can’t be used as inputs.

Rational Expressions

PQ

Page 31: 52 rational expressions

DomainThe domain of a formula is the set of all the numbers that we may use as input values for x. Because the denominator of a fraction can’t be 0, therefore for the rational formulas the zeroes of the denominator Q can’t be used as inputs.in other words, the domain of are all the numbers except where Q = 0.

Rational Expressions

PQ

PQ

Page 32: 52 rational expressions

Domain

b. Determine the domain of the formula

The domain of a formula is the set of all the numbers that we may use as input values for x. Because the denominator of a fraction can’t be 0, therefore for the rational formulas the zeroes of the denominator Q can’t be used as inputs.in other words, the domain of are all the numbers except where Q = 0.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

PQ

PQ

Page 33: 52 rational expressions

Domain

b. Determine the domain of the formula

The domain of a formula is the set of all the numbers that we may use as input values for x. Because the denominator of a fraction can’t be 0, therefore for the rational formulas the zeroes of the denominator Q can’t be used as inputs.in other words, the domain of are all the numbers except where Q = 0.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

x3 – 2x2 + 3xx2 + 4x + 3

Factor expression first.

= x(x + 2)(x – 1)(x + 3)(x + 1)

PQ

PQ

Page 34: 52 rational expressions

Domain

b. Determine the domain of the formula

The domain of a formula is the set of all the numbers that we may use as input values for x. Because the denominator of a fraction can’t be 0, therefore for the rational formulas the zeroes of the denominator Q can’t be used as inputs.in other words, the domain of are all the numbers except where Q = 0.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

x3 – 2x2 + 3xx2 + 4x + 3

Factor expression first.

= x(x + 2)(x – 1)(x + 3)(x + 1)

Hence we can’t have

PQ

PQ

(x + 3)(x + 1) = 0

Page 35: 52 rational expressions

Domain

b. Determine the domain of the formula

The domain of a formula is the set of all the numbers that we may use as input values for x. Because the denominator of a fraction can’t be 0, therefore for the rational formulas the zeroes of the denominator Q can’t be used as inputs.in other words, the domain of are all the numbers except where Q = 0.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

x3 – 2x2 + 3xx2 + 4x + 3

Factor expression first.

= x(x + 2)(x – 1)(x + 3)(x + 1)

Hence we can’t have

PQ

PQ

(x + 3)(x + 1) = 0so that the domain is the set of all the numbers except –1 and –3.

Page 36: 52 rational expressions

EvaluationIt is often easier to evaluate expressions in the factored form.

Rational Expressions

Page 37: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Page 38: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7,

Page 39: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8)

Page 40: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8)

34

Page 41: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8) =

34

18940

Page 42: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8) =

34

18940

Signs

Page 43: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8) =

34

18940

We use the factored form to determine the sign of an output.Signs

Page 44: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8) =

34

18940

We use the factored form to determine the sign of an output.Signs

d. Determine the signs (positive or negative) ofif x = ½,– 5/2 using the factored form.

x3 + x2 – 2xx2 + 4x + 3

Page 45: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8) =

34

18940

We use the factored form to determine the sign of an output.Signs

d. Determine the signs (positive or negative) ofif x = ½,– 5/2 using the factored form.

x3 + x2 – 2xx2 + 4x + 3

Plug in x = ½ into the above factored form and check the signs of each factor,

Page 46: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8) =

34

18940

We use the factored form to determine the sign of an output.Signs

d. Determine the signs (positive or negative) ofif x = ½,– 5/2 using the factored form.

x3 + x2 – 2xx2 + 4x + 3

Plug in x = ½ into the above factored form and check the signs of each factor, we get +( + )( – )

(+)(+)

Page 47: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8) =

34

18940

We use the factored form to determine the sign of an output.Signs

d. Determine the signs (positive or negative) ofif x = ½,– 5/2 using the factored form.

x3 + x2 – 2xx2 + 4x + 3

Plug in x = ½ into the above factored form and check the signs of each factor, we get = –, so it’s negative.+( + )( – )

(+)(+)

Page 48: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8) =

34

18940

We use the factored form to determine the sign of an output.Signs

d. Determine the signs (positive or negative) ofif x = ½,– 5/2 using the factored form.

x3 + x2 – 2xx2 + 4x + 3

Plug in x = ½ into the above factored form and check the signs of each factor, we get

Plug in x = –5/2 into the factored form we get –( – )( – )(+)( – )

= –, so it’s negative.+( + )( – )(+)(+)

Page 49: 52 rational expressions

Evaluation

c. Evaluate if x = 7 using the factored form.

It is often easier to evaluate expressions in the factored form.

Rational Expressions

x3 + x2 – 2xx2 + 4x + 3

Using the factored form x(x + 2)(x – 1)(x + 3)(x + 1)

Plug in x = 7, we get 7(9)(6)(10)(8) =

34

18940

We use the factored form to determine the sign of an output.Signs

d. Determine the signs (positive or negative) ofif x = ½,– 5/2 using the factored form.

x3 + x2 – 2xx2 + 4x + 3

Plug in x = ½ into the above factored form and check the signs of each factor, we get = –, so it’s negative.+( + )( – )

(+)(+)Plug in x = –5/2 into the factored form we get –( – )( – )

(+)( – ) = +so that the output is positive.

Page 50: 52 rational expressions

PNQN = =

1

Rational ExpressionsCancellation Law: Common factor may be cancelled, i.e.

PNQN

PQ

Page 51: 52 rational expressions

PNQN = =

1

Rational ExpressionsCancellation Law: Common factor may be cancelled, i.e.

PNQN

PQ

A rational expression is reduced (simplified) if all common factors are cancelled.

Page 52: 52 rational expressions

PNQN = =

1

Rational ExpressionsCancellation Law: Common factor may be cancelled, i.e.

PNQN

PQ

A rational expression is reduced (simplified) if all common factors are cancelled.To reduce (simplify) a rational expression, put the expression in the factored form then cancel the common factors.

Page 53: 52 rational expressions

PNQN = =

1

Rational ExpressionsCancellation Law: Common factor may be cancelled, i.e.

PNQN

PQ

A rational expression is reduced (simplified) if all common factors are cancelled.To reduce (simplify) a rational expression, put the expression in the factored form then cancel the common factors.Example B. Reduce the following expressions.

(x – 2)(x + 3)(x + 3)(x + 2)a.

b. x2 – 3x + 10 x2 – 3

Page 54: 52 rational expressions

PNQN = =

1

Rational ExpressionsCancellation Law: Common factor may be cancelled, i.e.

PNQN

PQ

A rational expression is reduced (simplified) if all common factors are cancelled.To reduce (simplify) a rational expression, put the expression in the factored form then cancel the common factors.Example B. Reduce the following expressions.

(x – 2)(x + 3)

It's already factored, proceed to cancel the common factor.(x + 3)(x + 2)

(x – 2)(x + 3)(x + 3)(x + 2)

a.

b. x2 – 3x + 10 x2 – 3

Page 55: 52 rational expressions

PNQN = =

1

Rational ExpressionsCancellation Law: Common factor may be cancelled, i.e.

PNQN

PQ

A rational expression is reduced (simplified) if all common factors are cancelled.To reduce (simplify) a rational expression, put the expression in the factored form then cancel the common factors.Example B. Reduce the following expressions.

(x – 2)(x + 3)

1 = x – 2

x + 2

It's already factored, proceed to cancel the common factor.(x + 3)(x + 2)

(x – 2)(x + 3)(x + 3)(x + 2) which is reduced.

a.

b. x2 – 3x + 10 x2 – 3

Page 56: 52 rational expressions

PNQN = =

1

Rational ExpressionsCancellation Law: Common factor may be cancelled, i.e.

PNQN

PQ

A rational expression is reduced (simplified) if all common factors are cancelled.To reduce (simplify) a rational expression, put the expression in the factored form then cancel the common factors.Example B. Reduce the following expressions.

(x – 2)(x + 3)

1 = x – 2

x + 2

It's already factored, proceed to cancel the common factor.(x + 3)(x + 2)

(x – 2)(x + 3)(x + 3)(x + 2) which is reduced.

a.

b. x2 – 3x + 10 x2 – 3

This is in the factored form.

Page 57: 52 rational expressions

PNQN = =

1

Rational ExpressionsCancellation Law: Common factor may be cancelled, i.e.

PNQN

PQ

A rational expression is reduced (simplified) if all common factors are cancelled.To reduce (simplify) a rational expression, put the expression in the factored form then cancel the common factors.Example B. Reduce the following expressions.

(x – 2)(x + 3)

1 = x – 2

x + 2

It's already factored, proceed to cancel the common factor.(x + 3)(x + 2)

(x – 2)(x + 3)(x + 3)(x + 2) which is reduced.

a.

b. x2 – 3x + 10 x2 – 3

This is in the factored form. There are no common factors so it’s already reduced.

Page 58: 52 rational expressions

Rational Expressionsc. x2 – 1

x2 – 3x+ 2

Page 59: 52 rational expressions

Rational Expressionsc. x2 – 1

x2 – 3x+ 2

Factor then cancel

Page 60: 52 rational expressions

Rational Expressionsc. x2 – 1

x2 – 3x+ 2x2 – 1

x2 – 3x+ 2= (x – 1)(x + 1) (x – 1)(x – 2)Factor then cancel

Page 61: 52 rational expressions

Rational Expressionsc. x2 – 1

x2 – 3x+ 2x2 – 1

x2 – 3x+ 2= (x – 1)(x + 1) (x – 1)(x – 2)

1 Factor then cancel

Page 62: 52 rational expressions

Rational Expressionsc. x2 – 1

x2 – 3x+ 2x2 – 1

x2 – 3x+ 2= (x – 1)(x + 1) (x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Page 63: 52 rational expressions

Rational Expressions

Only factors may be canceled.

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Page 64: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Page 65: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Page 66: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

For example, x2 + 1 x2 – 2 = x2 + 1

x2 – 2

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Page 67: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

For example, x2 + 1 x2 – 2 = x2 + 1

x2 – 2

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Cancellation of Opposite Factors

Page 68: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

For example, x2 + 1 x2 – 2 = x2 + 1

x2 – 2

The opposite of a quantity x is the –x.

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Cancellation of Opposite Factors

Page 69: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

For example, x2 + 1 x2 – 2 = x2 + 1

x2 – 2

The opposite of a quantity x is the –x. original: y -z x – y v – 4u – 2w opposite:

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Cancellation of Opposite Factors

Page 70: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

For example, x2 + 1 x2 – 2 = x2 + 1

x2 – 2

The opposite of a quantity x is the –x. original: y -z x – y v – 4u – 2w opposite: -y

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Cancellation of Opposite Factors

Page 71: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

For example, x2 + 1 x2 – 2 = x2 + 1

x2 – 2

The opposite of a quantity x is the –x. original: y -z x – y v – 4u – 2w opposite: -y z

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Cancellation of Opposite Factors

Page 72: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

For example, x2 + 1 x2 – 2 = x2 + 1

x2 – 2

The opposite of a quantity x is the –x. original: y -z x – y v – 4u – 2w opposite: -y z -x + y or y – x

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Cancellation of Opposite Factors

Page 73: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

For example, x2 + 1 x2 – 2 = x2 + 1

x2 – 2

The opposite of a quantity x is the –x. original: y -z x – y v – 4u – 2w opposite: -y z -x + y or y – x -v + 4u + 2w or …

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Cancellation of Opposite Factors

Page 74: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

For example, x2 + 1 x2 – 2 = x2 + 1

x2 – 2Cancellation of Opposite Factors

The opposite of a quantity x is the –x.

While identical factors cancel to be 1, opposite factors cancel to be –1,

original: y -z x – y v – 4u – 2w opposite: -y z -x + y or y – x -v + 4u + 2w or …

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Page 75: 52 rational expressions

Rational Expressions

Only factors may be canceled. It is wrong to cancel terms, i.e. P + Q P + R = P + Q

P + R

For example, x2 + 1 x2 – 2 = x2 + 1

x2 – 2

The opposite of a quantity x is the –x.

While identical factors cancel to be 1, opposite factors cancel to be –1, in symbol,

original: y -z x – y v – 4u – 2w opposite: -y z -x + y or y – x -v + 4u + 2w or …

x –x = –

1.

c. x2 – 1 x2 – 3x+ 2

x2 – 1 x2 – 3x+ 2= (x – 1)(x + 1)

(x – 1)(x – 2)

1 = x + 1

x – 2Factor then cancel

Cancellation of Opposite Factors

Page 76: 52 rational expressions

Example C. 2y

–2ya.

Rational Expressions

Page 77: 52 rational expressions

Example C. 2y

–2y =-1

–1a.

Rational Expressions

Page 78: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1a.

b.

Rational Expressions

Page 79: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1

a.

b.

Rational Expressions

Page 80: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

Page 81: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.

Page 82: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

Page 83: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y)

Page 84: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y) or –x – 3y

x – 3y

Page 85: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y) or –x – 3y

x – 3y

d. 4 – x2

x2 – x – 2

Page 86: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y) or –x – 3y

x – 3y

d. 4 – x2

x2 – x – 2 = (2 – x)(2 + x)(x + 1)(x – 2)

Page 87: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y) or –x – 3y

x – 3y

d. 4 – x2

x2 – x – 2 = (2 – x)(2 + x)(x + 1)(x – 2)

-1

Page 88: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y) or –x – 3y

x – 3y

d. 4 – x2

x2 – x – 2 = (2 – x)(2 + x)(x + 1)(x – 2)

-1= –(2 + x)

x + 1 or –2 – x x + 1

Page 89: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y) or –x – 3y

x – 3y

d. 4 – x2

x2 – x – 2 = (2 – x)(2 + x)(x + 1)(x – 2)

-1= –(2 + x)

x + 1 or –2 – x x + 1

In the case of polynomials in one variable x, if the highestdegree term is negative, we may factor out the negative sign then factor the expressions.

Page 90: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y) or –x – 3y

x – 3y

d. 4 – x2

x2 – x – 2 = (2 – x)(2 + x)(x + 1)(x – 2)

-1= –(2 + x)

x + 1 or –2 – x x + 1

–x2 + 4–x2 + x + 2

Example D. Pull out the “–” first then reduce.

In the case of polynomials in one variable x, if the highestdegree term is negative, we may factor out the negative sign then factor the expressions.

Page 91: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y) or –x – 3y

x – 3y

d. 4 – x2

x2 – x – 2 = (2 – x)(2 + x)(x + 1)(x – 2)

-1= –(2 + x)

x + 1 or –2 – x x + 1

In the case of polynomials in one variable x, if the highestdegree term is negative, we may factor out the negative sign then factor the expressions.

–x2 + 4–x2 + x + 2 =

Example D. Pull out the “–” first then reduce. –(x2 – 4)

–(x2 – x – 2)

Page 92: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y) or –x – 3y

x – 3y

d. 4 – x2

x2 – x – 2 = (2 – x)(2 + x)(x + 1)(x – 2)

-1= –(2 + x)

x + 1 or –2 – x x + 1

–x2 + 4–x2 + x + 2 = (x – 2)(x + 2)

(x + 1)(x – 2)=

Example D. Pull out the “–” first then reduce. –(x2 – 4)

–(x2 – x – 2)

In the case of polynomials in one variable x, if the highestdegree term is negative, we may factor out the negative sign then factor the expressions.

Page 93: 52 rational expressions

b(x – y)a(y – x)

Example C. 2y

–2y =-1

–1-1= –b

a

a.

b.

Rational Expressions

(x – 2y)(x + 3y) (x – 3y)(2y – x)

c.-1

= –(x + 3y) (x – 3y) or –x – 3y

x – 3y

d. 4 – x2

x2 – x – 2 = (2 – x)(2 + x)(x + 1)(x – 2)

-1= –(2 + x)

x + 1 or –2 – x x + 1

–x2 + 4–x2 + x + 2 = (x – 2)(x + 2)

(x + 1)(x – 2)=

Example D. Pull out the “–” first then reduce. –(x2 – 4)

–(x2 – x – 2) = x + 2 x + 1

In the case of polynomials in one variable x, if the highestdegree term is negative, we may factor out the negative sign then factor the expressions.

Page 94: 52 rational expressions

Rational ExpressionsTo summarize, a rational expression is reduced (simplified) if all common factors are cancelled.Following are the steps for reducing a rational expression.1. Factor the top and bottom completely. (If present, factor the “ – ” from the leading term)2. Cancel the common factors: -cancel identical factors to be 1 -cancel opposite factors to be –1

Page 95: 52 rational expressions

Ex. A. Write the following expressions in factored form. List all the distinct factors of the numerator and the denominator of each expression.

1.

Rational Expressions

2x + 3 x + 3 2. 4x + 6

2x + 6 3. x2 – 4 2x + 4

4. x2 + 4x2 + 4x 5. x2 – 2x – 3

x2 + 4x 6. x3 – 2x2 – 8xx2 + 2x – 3

7. Find the zeroes and list the domain of x2 – 2x – 3x2 + 4x

8. Use the factored form to evaluate x2 – 2x – 3x2 + 4x

with x = 7, ½, – ½, 1/3. 9. Determine the signs of the outputs of x2 – 2x – 3

x2 + 4xwith x = 4, –2, 1/7, 1.23.For problems 10, 11, and 12, answer the same questions

as problems 7, 8 and 9 with the formula .x3 – 2x2 – 8xx2 + 2x – 3

Page 96: 52 rational expressions

Ex. B. Reduce the following expressions. If it’s already reduced, state this. Make sure you do not cancel any terms and make sure that you look for the opposite cancellation.

13.

Rational Expressions

2x + 3 x + 3

20. 4x + 6 2x + 3

22. 23. 24.

21.

3x – 12x – 4

12 – 3xx – 4

4x + 6 –2x – 3

3x + 12x – 4

25. 4x – 6 –2x – 3

14. x + 3 x – 3 15. x + 3

–x – 3

16. x + 3x – 3

17. x – 3 3 – x 18. 2x – 1

1 + 2x

19. 2x – 1 1 – 2x

26. (2x – y)(x – 2y)(2y + x)(y – 2x) 27. (3y + x)(3x –y)

(y – 3x)(–x – 3y)

28. (2u + v – w)(2v – u – 2w)(u – 2v + 2w)(–2u – v – w) 29. (a + 4b – c)(a – b – c)

(c – a – 4b)(a + b + c)

Page 97: 52 rational expressions

30.

Rational Expressions

37.

x2 – 1x2 + 2x – 3

36. 38. x – x2

39. x2 – 3x – 4

31. 32.

33. 34. 35.

40. 41. x3 – 16x

x2 + 4 2x + 4

x2 – 4x + 4

x2 – 4x2– 2x

x2 – 9x2 + 4x + 3

x2 – 4 2x + 4

x2 + 3x + 2x2 – x – 2 x2 + x – 2

x2 – x – 6x2 – 5x + 6

x2 – x – 2x2 + x – 2

x2 – 5x – 6

x2 + 5x – 6x2 + 5x + 6

x3 – 8x2 – 20x

46.45. 47. 9 – x2

42. 43. 44. x2 – 2x9 – x2

x2 + 4x + 3– x2 – x + 2

x3 – x2 – 6x–1 + x2

–x2 + x + 2x2 – x – 2

– x2 + 5x – 61 – x2

x2 + 5x – 6

49.48. 50.xy – 2y + x2 – 2xx2 – y2 x3 – 100x

x2 – 4xy + x – 4yx2 – 3xy – 4y2

Ex. C. Reduce the following expressions. If it’s already reduced, state this. Make sure you do not cancel any terms and make sure that you look for the opposite cancellation.


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