Integral of $$$- \frac{3 x}{7 \pi}$$$

Find $$$\int \left(- \frac{3 x}{7 \pi}\right)\, dx$$$.

Apply the constant multiple rule $$$\int c f{\left(x \right)}\, dx = c \int f{\left(x \right)}\, dx$$$ with $$$c=- \frac{3}{7 \pi}$$$ and $$$f{\left(x \right)} = x$$$:

$${\color{red}{\int{\left(- \frac{3 x}{7 \pi}\right)d x}}} = {\color{red}{\left(- \frac{3 \int{x d x}}{7 \pi}\right)}}$$

Apply the power rule $$$\int x^{n}\, dx = \frac{x^{n + 1}}{n + 1}$$$ $$$\left(n \neq -1 \right)$$$ with $$$n=1$$$:

$$- \frac{3 {\color{red}{\int{x d x}}}}{7 \pi}=- \frac{3 {\color{red}{\frac{x^{1 + 1}}{1 + 1}}}}{7 \pi}=- \frac{3 {\color{red}{\left(\frac{x^{2}}{2}\right)}}}{7 \pi}$$

Therefore,

$$\int{\left(- \frac{3 x}{7 \pi}\right)d x} = - \frac{3 x^{2}}{14 \pi}$$

Add the constant of integration:

$$\int{\left(- \frac{3 x}{7 \pi}\right)d x} = - \frac{3 x^{2}}{14 \pi}+C$$

$$$\int \left(- \frac{3 x}{7 \pi}\right)\, dx = - \frac{3 x^{2}}{14 \pi} + C$$$A