Integral of $$$1 - 6 e^{2 x}$$$

Find $$$\int \left(1 - 6 e^{2 x}\right)\, dx$$$.

Integrate term by term:

$${\color{red}{\int{\left(1 - 6 e^{2 x}\right)d x}}} = {\color{red}{\left(\int{1 d x} - \int{6 e^{2 x} d x}\right)}}$$

Apply the constant rule $$$\int c\, dx = c x$$$ with $$$c=1$$$:

$$- \int{6 e^{2 x} d x} + {\color{red}{\int{1 d x}}} = - \int{6 e^{2 x} d x} + {\color{red}{x}}$$

Apply the constant multiple rule $$$\int c f{\left(x \right)}\, dx = c \int f{\left(x \right)}\, dx$$$ with $$$c=6$$$ and $$$f{\left(x \right)} = e^{2 x}$$$:

$$x - {\color{red}{\int{6 e^{2 x} d x}}} = x - {\color{red}{\left(6 \int{e^{2 x} d x}\right)}}$$

Let $$$u=2 x$$$.

Then $$$du=\left(2 x\right)^{\prime }dx = 2 dx$$$ (steps can be seen »), and we have that $$$dx = \frac{du}{2}$$$.

Therefore,

$$x - 6 {\color{red}{\int{e^{2 x} d x}}} = x - 6 {\color{red}{\int{\frac{e^{u}}{2} d u}}}$$

Apply the constant multiple rule $$$\int c f{\left(u \right)}\, du = c \int f{\left(u \right)}\, du$$$ with $$$c=\frac{1}{2}$$$ and $$$f{\left(u \right)} = e^{u}$$$:

$$x - 6 {\color{red}{\int{\frac{e^{u}}{2} d u}}} = x - 6 {\color{red}{\left(\frac{\int{e^{u} d u}}{2}\right)}}$$

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

$$x - 3 {\color{red}{\int{e^{u} d u}}} = x - 3 {\color{red}{e^{u}}}$$

Recall that $$$u=2 x$$$:

$$x - 3 e^{{\color{red}{u}}} = x - 3 e^{{\color{red}{\left(2 x\right)}}}$$

Therefore,

$$\int{\left(1 - 6 e^{2 x}\right)d x} = x - 3 e^{2 x}$$

Add the constant of integration:

$$\int{\left(1 - 6 e^{2 x}\right)d x} = x - 3 e^{2 x}+C$$

$$$\int \left(1 - 6 e^{2 x}\right)\, dx = \left(x - 3 e^{2 x}\right) + C$$$A