Chapter 2.3

Slope

Warm – Up!

Put the following equation in standard form. ½ x = 3y - 8

Find the X and Y intercepts and graph.

4Y- 2y = 6

Use slope to graph a line:

Find the slope of the line that passes through (0, 0) and (–5, 6). Then graph the line.

xx

yym

05

06

m

5

6

m

Positive Slope:

f(x)=3x +2

-8 -6 -4 -2 2 4 6 8

-5

5

x

y

When the slope shows as 3/1 then the rise is positive or up and the run is to the right. Therefore the slope goes upward from left to right.

Negative Slope:

f(x)=-4x+3

-8 -6 -4 -2 2 4 6 8

-5

5

x

yWhen the slope is

-4/1 then the rise is negative and going down and the run is to the right. Therefore the line goes downward from left to right.

Zero Slope:

f(x)=5

-8 -6 -4 -2 2 4 6 8

-5

5

x

yWhen there is no x value in the equation, then there is no slope. Notice that there is no rise, but there is run. Therefore, there is a zero divided by a number.

M = 0/#

Undefined Slope:

x=3

-8 -6 -4 -2 2 4 6 8

-5

5

x

y

In this case there is rise, but no run, therefore the number is divided by zero and cannot be done, so it is undefinable.

#/0 = m

Parallel and Perpendicular Lines:

Parallel Lines have the same slope

f(x)=3x+4

f(x)=3x-5

-8 -6 -4 -2 2 4 6 8

-5

5

x

y

Perpendicular Lines have opposite reciprocal slopes

f(x)=3x+2

f(x)=(-1/3)x +2

-8 -6 -4 -2 2 4 6 8

-5

5

x

y

Tonight’s Homework:

Page 72/73

(15-21 odd) (31-35 odd)

(43-47 odd)

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