Answer
$h'(x) = -\dfrac{1}{2}x^{-3/2}+21x^{-5/2}$
Work Step by Step
In order to derivate this function you have to apply the power rule:
$\dfrac{d}{dx}(x^n)=nx^{n-1}$
$h'(x) = -\dfrac{1}{2}x^{-3/2}-14(-\dfrac{3}{2})x^{-5/2}$
$h'(x) = -\dfrac{1}{2}x^{-3/2}+21x^{-5/2}$