The graph of \(f\) (blue) and the graph of its derivative \(f'\) (red) are shown. Where is \(f\) increasing and decreasing, and where does \(f\) have a local maximum or a local minimum? Explain using \(f'\).
\(f'=0\) at \(x=-1\) and \(x=1\). At \(x=-1\), \(f'\) changes from \(+\) to \(-\): a **local maximum** (\(f(-1)=2\)). At \(x=1\), \(f'\) changes from \(-\) to \(+\): a **local minimum** (\(f(1)=-2\)). Here \(f(x)=x^3-3x\) and \(f'(x)=3x^2-3\).