Integral de $$$- \frac{3}{x - 3}$$$

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

Aplica la regla del factor constante $$$\int c f{\left(x \right)}\, dx = c \int f{\left(x \right)}\, dx$$$ con $$$c=-3$$$ y $$$f{\left(x \right)} = \frac{1}{x - 3}$$$:

$${\color{red}{\int{\left(- \frac{3}{x - 3}\right)d x}}} = {\color{red}{\left(- 3 \int{\frac{1}{x - 3} d x}\right)}}$$

Sea $$$u=x - 3$$$.

Entonces $$$du=\left(x - 3\right)^{\prime }dx = 1 dx$$$ (los pasos pueden verse »), y obtenemos que $$$dx = du$$$.

Entonces,

$$- 3 {\color{red}{\int{\frac{1}{x - 3} d x}}} = - 3 {\color{red}{\int{\frac{1}{u} d u}}}$$

La integral de $$$\frac{1}{u}$$$ es $$$\int{\frac{1}{u} d u} = \ln{\left(\left|{u}\right| \right)}$$$:

$$- 3 {\color{red}{\int{\frac{1}{u} d u}}} = - 3 {\color{red}{\ln{\left(\left|{u}\right| \right)}}}$$

Recordemos que $$$u=x - 3$$$:

$$- 3 \ln{\left(\left|{{\color{red}{u}}}\right| \right)} = - 3 \ln{\left(\left|{{\color{red}{\left(x - 3\right)}}}\right| \right)}$$

Por lo tanto,

$$\int{\left(- \frac{3}{x - 3}\right)d x} = - 3 \ln{\left(\left|{x - 3}\right| \right)}$$

Añade la constante de integración:

$$\int{\left(- \frac{3}{x - 3}\right)d x} = - 3 \ln{\left(\left|{x - 3}\right| \right)}+C$$

$$$\int \left(- \frac{3}{x - 3}\right)\, dx = - 3 \ln\left(\left|{x - 3}\right|\right) + C$$$A