Critical Numbers

Find and classify the critical points of the following function

$f(x) = x^3 - 3x^2 - 9x + 2$

$y = x^{2/3}(2-x)$

Find: A. The critical values of x? B. The x coordinate of the local maximum

Find the critical numbers of the function

$f(x) = x^2 - 4x$

Find the critical numbers for the following function $f(x) = x^{\frac{2}{3}}$