Exercise 21 Page 660

We are asked to find the slope of a line. Observing the given graph, we can see that the line passes through the points (-4,5) 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 -1. Similarly, the run, or change in x, is 4. slope=rise/run ⇔ m=-1/4=- 1/4 We can confirm this 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 ( -4,5) & ( 0,4)

m=5- 4/- 4- 0

SubTerms

Subtract terms

m=1/- 4

MoveNegNumToFrac

Put minus sign in front of fraction

m=-1/4

We obtained the same number as before. We can be sure the slope is - 14.