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Academic Content Standards Patterns, Functions, and Algebra Standard 8 th Grade 1. Relate the...

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Academic Content Standards Patterns, Functions, and Algebra Standard 8 th Grade 1. Relate the various representations of a relationship; i.e., relate table to graph, description and symbolic form. 4. Extend the uses of variables to include covariants where y depends on x. 6. Describe the relationship between the graph of a line and its equation, including being able to explain the meaning of slope as a constant rate of change and y-intercept in real-world problems.
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Academic Content Standards

Patterns, Functions, and Algebra Standard 8th Grade

1. Relate the various representations of a relationship; i.e., relate table to graph, description and symbolic form.

• 4. Extend the uses of variables to include covariants where y dependson x.

• 6. Describe the relationship between the graph of a line and itsequation, including being able to explain the meaning of slope as aconstant rate of change and y-intercept in real-world problems.

Academic Content Standards

Patterns, Functions, and Algebra Standard 8th Grade

• 13. Compute and interpret slope, midpoint and distance given a set ofordered pairs.

• 15. Describe and compare how changes in an equation affects therelated graphs; e.g., for a linear equation changing the coefficient ofx affects the slope and changing the constant affects the intercepts.

• 16. Use graphing calculators or computers to analyze change; e.g.,interest compounded over time as a nonlinear growth pattern.

Solve the following equation for “y”.

Solve the following equation for “y”.

24

3 xy

You just put the equation in slope-intercept form!!!

24

3 xy

5.3 Equation of Lines

Objectives:

1. Discover the slope intercept form of the equation of a line.

325

9 cf

This graph shows the relationship between degrees Celsius and degrees Fahrenheit.

This is the graph of :

325

9 xy

To convert from C to F, pick some degrees Celsius to convert:

325

9 cf

Let’s say you want to convert 16°C to °F.

325

9 cf

Find 16°C

on the x axis

325

9 cf

Go straight up from 16° to the line.

325

9 cf

From the line, go to the “f” axis. This is equal to 16°C in Fahrenheit!

16 °C = 61°F

325

9 cf

16°C is equal to almost 61° Fahrenheit

16 °C = 61°F

You plug 16°C into the equation and see what you

get.

325

9 cf 32

1

)16(

5

9f

328.28 f 8.60f

You will now be asked several questions about the

graph of:

325

9 cf

3°C= ___°F37

Plug 3°C into the equation and see what you get.

325

9 cf 32

1

)3(

5

9f

324.5 f 4.37f

9°C= ___°F48

42°C= _____°F107.6

42°F= _____°C5

100°F= ____°C38

xy

-2-4

-1-1

051

228

Complete the chart and calculate the slope of the line.

Compare your calculated slope with the equation of the line. Do you see a relationship?

The Slope Formula

•y2 - y1

x2 - x1x3x+2

-2-4

-1-1

051

2

1

3

Compare your calculated slope with the equation of the line. Do you see a relationship?

x3x+2

-2-4

-1-1

051

2

1

3

The slope is the number in front of the “x”.

When an equation is in slope-intercept form:

Now look at the graph of each line. Look at where the graph crosses the “y” axis.

What is the significance of this number in the equation?

This is the y-intercept (where the graph crosses the “y” axis.

When an equation is in slope-intercept form:

Slope-Intercept Conjecture:

y=mx+b

What is the equation of the line in slope-intercept form?

m =

b =

4

3

-2

24

3 xy

What is the equation of the line in slope-intercept form?

m =

b =

3

5

2

35

2 xy

What is the equation of the line in slope-intercept form?

m =

b =

4

2

1

42

1 xy

Graph the equation…. First calculate the slope and y-int.

m =

b =

-4

43

2 xy

3

2

Plot the y-intercept.

m =

b =

-4

43

2 xy

3

2

Apply slope from y-intercept.

m =

b =

-4

43

2 xy

3

2

Draw line through two points.

m =

b =

-4

43

2 xy

3

2

Graph each equation:

m =

b =

1

18

7 xy

8

7

Graph each equation:

m =

b =

6

y=-4x+6

-4

True or False. The slope of the line below is .

5

2

True or False. The y-intercept of the line is -4.

True or False. The equation of the line is:

45

2 xy

Homework

Page 275 #’s:

15-45 odds


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