Exercise 9 Page 157

Equations written in slope-intercept form follow a specific format. y= mx+ b In this form, m is the slope and b is the y-intercept. We need to identify these values using the graph.

y-intercept

The y-intercept is the y-value where the line crosses the y-axis.

We can see that the function intercepts the y-axis at (0, - 6). This means that the value of b is - 6. y= mx+( - 6)

Slope

To find the slope, we will trace along the line on the given graph until we find a lattice point, which is a point that lies perfectly on the grid lines. Doing so, we can identify the slope m using the rise and run of the graph.

Here we have identified the point (2,2) as our other point. Traveling from the y-intercept to this point requires that we move 2 steps horizontally in the positive direction and 8 steps vertically in the positive direction. rise/run=8/2 ⇔ m= 4

Writing the Equation

Now that we have the slope and the y-intercept, we can write our final equation. y= 4x+( - 6) ⇔ y = 4x - 6