4e^(x^3+3x) + 3x

things in parenthesis are an exponent

4e^(x^3+3x) + 3x

things in parenthesis are an exponent

the derivative is the difference quotient as h approaches 0

To find f'(x)

You need to find what \frac{f(x+h)-f(x)}{h} and take the limit as h approaches 0.

If your past the point of taking difference quotients to find the derivative, then there are general rules here that you have to follow. The following you will need here is that

\frac{d}{dx}A*x = A
\frac{d}{dx}x^n = n*x^{n-1}
\frac{d}{dx}e^x^n = ne^x^n

Don't forget about chain rule!