Answer
$-\frac{C4^{\frac{C}{x}} ln 4}{x^{2}}$
Work Step by Step
$\frac{d}{dx}G(x)=\frac{d}{dx}4^{\frac{C}{x}}$
$=4^{\frac{C}{x}} ln 4 \frac{d}{dx}(\frac{C}{x})$
$=-4^{\frac{C}{x}} ln 4 C(\frac{1}{x^{2}})$
Hence, $-\frac{C4^{\frac{C}{x}} ln 4}{x^{2}}$