Maclaurin’s formula
On the graph of ff,
f′(x)>0f^{\prime}(x)>0 gives ff increasing;
f′(x)<0f^{\prime}(x)<0 gives ff decreasing;
f′(x)=0f^{\prime}(x)=0 gives a stationary point.
At a stationary point aa,
f′′(a)>0f^{\prime\prime}(a)>0 gives a local minimum;
f′′(a)<0f^{\prime\prime}(a)<0 gives a local maximum.