Find the local maxima and local minima, if any, of the following functions. Find also the local maximum and the local minimum values, as the case may be: $ f (x) =x^3-6x^2+9x+15$

Question

$\begin{array}{1 1}Minimum = 15\; Maximum = 20 \\ Minimum = 17\; Maximum = 19 \\ Minimum = 15\; Maximum = 19 \\ Minimum = 15 \;Maximum = 18 \end{array} $