# Math Help - derivatives

1. ## derivatives

let f be the function given by f(x)=2e^4x^2. for what value of x is the slope of the line tangent to the graph of f at (x,f(x)) equal to 3?

2. $
\begin{array}{l}
\frac{{df}}{{dx}} = \frac{d}{{dx}}2e^{4x^2 } \\
u = 4x^2 \\
\frac{{df}}{{dx}} = \frac{{df}}{{du}}\frac{{du}}{{dx}} = 2e^u 8x = 16xe^{4x^2 } \\
\end{array}
$

3. I understand how to get the derivative but now what?