The question is to estimate the solution to the equation f(x)=-1. A graph is shown...

We see from the graph the point (3,-1) lies on the graph of f, so the value of f at -3 is -1. In other words, the point on the graph of f, when x = -3 the graph lies about -1 unit below the x-axis, so we estimate that
f(-3)-1
Also the point (4,-1) lies on the graph of f, so the value of f at 4 is -1.(n other words, the point on the graph of f, when x = 4 the graph lies about -1 unit below the x-axi s, so we estimate that
f(4)=-1.