Integral dari $$$\frac{1}{1 - x}$$$

Temukan $$$\int \frac{1}{1 - x}\, dx$$$.

Misalkan $$$u=1 - x$$$.

Kemudian $$$du=\left(1 - x\right)^{\prime }dx = - dx$$$ (langkah-langkah dapat dilihat di »), dan kita memperoleh $$$dx = - du$$$.

Integralnya menjadi

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

Terapkan aturan pengali konstanta $$$\int c f{\left(u \right)}\, du = c \int f{\left(u \right)}\, du$$$ dengan $$$c=-1$$$ dan $$$f{\left(u \right)} = \frac{1}{u}$$$:

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

Integral dari $$$\frac{1}{u}$$$ adalah $$$\int{\frac{1}{u} d u} = \ln{\left(\left|{u}\right| \right)}$$$:

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

Ingat bahwa $$$u=1 - x$$$:

$$- \ln{\left(\left|{{\color{red}{u}}}\right| \right)} = - \ln{\left(\left|{{\color{red}{\left(1 - x\right)}}}\right| \right)}$$

Oleh karena itu,

$$\int{\frac{1}{1 - x} d x} = - \ln{\left(\left|{x - 1}\right| \right)}$$

Tambahkan konstanta integrasi:

$$\int{\frac{1}{1 - x} d x} = - \ln{\left(\left|{x - 1}\right| \right)}+C$$

$$$\int \frac{1}{1 - x}\, dx = - \ln\left(\left|{x - 1}\right|\right) + C$$$A