The graphs of $y=f(x)$ and $y=f'(x)$ are closely related. Since $f'(a)$ represents the slope of the tangent line to $y=f(x)$ at $(a, f(a))$, the slope of $y=f(x)$ at $x$ is the same as the height of the graph $y=f'(x)$ at that $x$, as illustrated below.