## Calculus (3rd Edition)

$$y'=7^{4x-x^2} (4-2x) \ln 7.$$
Recall that the derivative of $a^{f(x)}$ is $a^{f(x)} f'(x)\ln a$ Since $y=7^{4x-x^2}$, we have $$y'=7^{4x-x^2} (4-2x) \ln 7.$$