Integral of $$$e^{6 x}$$$

Let $$$u=6 x$$$.

Then $$$du=\left(6 x\right)^{\prime }dx = 6 dx$$$ (steps can be seen »), and we have that $$$dx = \frac{du}{6}$$$.

The integral becomes

$${\color{red}{\int{e^{6 x} d x}}} = {\color{red}{\int{\frac{e^{u}}{6} d u}}}$$

Apply the constant multiple rule $$$\int c f{\left(u \right)}\, du = c \int f{\left(u \right)}\, du$$$ with $$$c=\frac{1}{6}$$$ and $$$f{\left(u \right)} = e^{u}$$$:

$${\color{red}{\int{\frac{e^{u}}{6} d u}}} = {\color{red}{\left(\frac{\int{e^{u} d u}}{6}\right)}}$$

The integral of the exponential function is $$$\int{e^{u} d u} = e^{u}$$$:

$$\frac{{\color{red}{\int{e^{u} d u}}}}{6} = \frac{{\color{red}{e^{u}}}}{6}$$

Recall that $$$u=6 x$$$:

$$\frac{e^{{\color{red}{u}}}}{6} = \frac{e^{{\color{red}{\left(6 x\right)}}}}{6}$$

Therefore,

$$\int{e^{6 x} d x} = \frac{e^{6 x}}{6}$$

Add the constant of integration:

$$\int{e^{6 x} d x} = \frac{e^{6 x}}{6}+C$$

$$$\int e^{6 x}\, dx = \frac{e^{6 x}}{6} + C$$$A