Integral de $$$\frac{x^{2} + 6 x + 9}{x + 3}$$$

Encontre $$$\int \frac{x^{2} + 6 x + 9}{x + 3}\, dx$$$.

Seja $$$u=x + 3$$$.

Então $$$du=\left(x + 3\right)^{\prime }dx = 1 dx$$$ (veja os passos »), e obtemos $$$dx = du$$$.

Assim,

$${\color{red}{\int{\frac{x^{2} + 6 x + 9}{x + 3} d x}}} = {\color{red}{\int{u d u}}}$$

Aplique a regra da potência $$$\int u^{n}\, du = \frac{u^{n + 1}}{n + 1}$$$ $$$\left(n \neq -1 \right)$$$ com $$$n=1$$$:

$${\color{red}{\int{u d u}}}={\color{red}{\frac{u^{1 + 1}}{1 + 1}}}={\color{red}{\left(\frac{u^{2}}{2}\right)}}$$

Recorde que $$$u=x + 3$$$:

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

Portanto,

$$\int{\frac{x^{2} + 6 x + 9}{x + 3} d x} = \frac{\left(x + 3\right)^{2}}{2}$$

Adicione a constante de integração:

$$\int{\frac{x^{2} + 6 x + 9}{x + 3} d x} = \frac{\left(x + 3\right)^{2}}{2}+C$$

$$$\int \frac{x^{2} + 6 x + 9}{x + 3}\, dx = \frac{\left(x + 3\right)^{2}}{2} + C$$$A