Question

Here’s a graph of a linear function. Write the equation that describes that function. Express it in slope-intercept form.

Answer 1

y = (1/3)x + 4

Explanation:

Two points on this straight line are (-9, 1) and (0, 4).

As we move from the first point to the second, x increases by 9 and y by 3. Thus, the slope of this line is m = rise / run = 3/9, or m = 1/3.

The y-intercept is easily read off the graph: it is (0, 4). Thus, b = 4 in the slope-intercept form of the equation of a straight line, y = mx + b:

y = (1/3)x + 4

This is the desired linear function.