$$ f(x) = (ax^2-3)^{\frac{1}{2}} $$
Nach Kettenregel:
$$ h = ax^2 -3 \quad h' = 2ax $$
$$ g = x^{\frac{1}{2}} \quad g' = \frac{1}{2}x^{-\frac{1}{2}} $$
Ableitung:
$$ f'(x) = \frac{1}{2}(ax^2 -3)^{-\frac{1}{2}} \cdot 2ax = \frac{ax}{\sqrt{ax^2-3}} $$
Hope this helps!