$\huge \begin{align} \int e^x \d{x} &= e^x +C \\ \int e^{ax} \d{x} &= \frac{1}{a}e^{ax} + C\\ \int a^x \d x &= \frac{a^x}{\ln a} + C \\ \end{align} $ >[!example] >$\huge \int 2^{\pi x}\d x $ >$\huge \begin{align} \let u &= \pi x \\ \let \d u &=\frac{\pi}{\d x} \\ \int 2^{\pi x}\d x &= \int \frac{2^u}{\pi} \d u \\ &= \frac{2^u}{\pi\ln 2} + C\\ &= \frac{2^{\pi x}}{\pi\ln 2} + C \end{align}$