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3-4 Using Formulas
Objective: Solve problems using formulas.
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5-Minute Check
Solve each equation. Check your solution.
1. x/3 = -6
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5-Minute Check
Solve each equation. Check your solution.
1. x/3 = -6 -18
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5-Minute Check
Solve each equation. Check your solution.
1. x/3 = -6
2. -3x = -6
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5-Minute Check
Solve each equation. Check your solution.
1. x/3 = -6
2. -3x = -6 2
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5-Minute Check
Solve each equation. Check your solution.
1. x/3 = -6
2. -3x = -6
3. x/-2 = -16
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5-Minute Check
Solve each equation. Check your solution.
1. x/3 = -6
2. -3x = -6
3. x/-2 = -16 32
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5-Minute Check
Solve each equation. Check your solution.
1. x/3 = -6
2. -3x = -6
3. x/-2 = -16
4. -2x = 16
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5-Minute Check
Solve each equation. Check your solution.
1. x/3 = -6
2. -3x = -6
3. x/-2 = -16
4. -2x = 16 -8
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5-Minute Check
Solve each equation. Check your solution.
1. x/3 = -6
2. -3x = -6
3. x/-2 = -16
4. -2x = 16
5. 12x = -156
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5-Minute Check
Solve each equation. Check your solution.
1. x/3 = -6
2. -3x = -6
3. x/-2 = -16
4. -2x = 16
5. 12x = -156 -13
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3-4 Using Formulas
A formula shows the relationship between certainquantities.
Variables are used to represent these qualities.
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3-4 Using Formulas
Write a formula for the diameter of a circle, given it radius r.
It is often helpful to draw a picture.
Let d = diameter.
Let r = radius
The radius is equal to half the diameter of a circle.
r = d
So, d = 2r.
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3-4 Using Formulas
Example
Use the formula d = 2r to find the radius of a circle that has a
diameter of 18 meters.
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3-4 Using Formulas
Example
Use the formula d = 2r to find the radius of a circle that has a
diameter of 18 meters.
d = 2r Diameter formula.
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3-4 Using Formulas
Example
Use the formula d = 2r to find the radius of a circle that has a
diameter of 18 meters.
d = 2r Diameter formula.18 = 2r Substitute 18 for d.
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3-4 Using Formulas
Example
Use the formula d = 2r to find the radius of a circle that has a
diameter of 18 meters.
d = 2r Diameter formula.18 = 2r Substitute 18 for d.
18/2 = 2r/2 Divide each side by 2.
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3-4 Using Formulas
Example
Use the formula d = 2r to find the radius of a circle that has a
diameter of 18 meters.
d = 2r Diameter formula.18 = 2r Substitute 18 for d.
18/2 = 2r/2 Divide each side by 2.
9 = r
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3-4 Using Formulas
Example
Use the formula d = 2r to find the radius of a circle that has a
diameter of 18 meters.
d = 2r Diameter formula.18 = 2r Substitute 18 for d.
18/2 = 2r/2 Divide each side by 2.
9 = r
A circle with a diameter of 18 meters has a radius of 9meters.
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3-4 Using Formulas
Integration
An equilateral triangle is a triangle whose three sides are all
equal in length. Give a formula for the perimeter of any
equilateral triangle.
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3-4 Using Formulas
Integration
An equilateral triangle is a triangle whose three sides are all
equal in length. Give a formula for the perimeter of any
equilateral triangle.
Answer: p = 3s where p = perimeter and s = length of each
side.