Hello guys.

I need quick help on these two problems from my math packet. One of them having to do with Derivatives and the other having to do with Integrals.

Here are the problems I need the most help in:

$\displaystyle f(x)= \sqrt{ e^{7x} + e^{-7x}}$

Mr F says: Use the chain rule. Let $\displaystyle {\color{red}u = e^{7x} + e^{-7x}}$.
and

$\displaystyle \int\frac{e^{\frac{4}{x^{2}}}}{6x^{3}}dx$

Mr F says: Make the sustitution $\displaystyle {\color{red}u = \frac{4}{x^2}}$.
I really appreciate the help!

Thank you all.