Integrating $3^{2x}$ ($\int 3^{2x} dx $) I am tring to integrate the following: $3^{2x}$
My working has been shown as the following
$$\int 3^{2x} dx $$
I used the substitution $u = 2x$, so 
$$\frac{du}{2} = dx $$
hence
$$\int 3^{2x} dx = \int 3^{u} \frac{du}{2} = \frac{1}{2}\int 3^{u} du $$ 
However, I can't go any further.
From this, I can't seem to prove the general result of  $\int a^{x} dx $ either.
Can someone help?
Thanks!

Hint: $\displaystyle\int{a^{mx}}\ dx=\dfrac{a^{mx}}{m\cdot\ln a}+c$
