The function f(x) is shown in the graph.
what is the equation for f(x)?

It's a linear graph, so we can use the slope-intercept form. Let's find the y-intercept first, which happens ar y = -3. Now let's find the slope. To do so, let's pick two points on the graph (relatively easy ones): (0, -3) and (5, -7). 

Let's find the slope:


Let's write it in slope-intercept form. Recall that slope-intercept form is:


Where m = slope and b = y-intercept. We have all the parts, so let's write it: