Exercise 12 Page 188

Observing the given graph, we can see that the line passes through the points (2,-2) and (0,4). One way to use a graph to find the slope of a line is to count out the change in x and y.

We can see that as the graph travels from left to right, the rise, or change in y, is 6. Similarly, the run, or change in x, is - 2. slope=rise/run ⇔ m=6/- 2=- 3 We can confirm this answer by using the Slope Formula. m = y_2-y_1/x_2-x_1 We will use the given points to solve for the slope.

m = y_2-y_1/x_2-x_1

SubstitutePoints

Substitute ( 2,-2) & ( 0,4)

m=4-( - 2)/0- 2

SubNeg

a-(- b)=a+b

m=4+2/0-2

AddSubTerms

Add and subtract terms

m=6/- 2

MoveNegNumToFrac

Put minus sign in front of fraction

m=-6/2

CalcQuot

Calculate quotient

m=- 3

We obtained the same number as before. We can be sure the slope is - 3.