Answer
$$ x=-3,5$$
Work Step by Step
To solve an equation set equal to zero using a graph, we see where the graph intersects the x-axis. Thus, we can use the reverse method, solving the equation by setting it equal to zero to see what the x-intercepts are. Doing this, we find:
$$ 0=x^2-2x-15 \\ 0=(x-5)(x+3) \\ x=-3,5$$