$$\displaystyle\frac{d}{d x } \left(12x- { x }^{ 2 } - \frac{ 3 }{ \sqrt{ x } } \right)$$
$-2x+12+\frac{3}{2x^{\frac{3}{2}}}$
$-2-\frac{9}{4x^{\frac{5}{2}}}$
