$$$\frac{\ln\left(x\right)}{x^{6}}$$$ 的积分

求$$$\int \frac{\ln\left(x\right)}{x^{6}}\, dx$$$。

对于积分$$$\int{\frac{\ln{\left(x \right)}}{x^{6}} d x}$$$，使用分部积分法$$$\int \operatorname{u} \operatorname{dv} = \operatorname{u}\operatorname{v} - \int \operatorname{v} \operatorname{du}$$$。

设 $$$\operatorname{u}=\ln{\left(x \right)}$$$ 和 $$$\operatorname{dv}=\frac{dx}{x^{6}}$$$。

则 $$$\operatorname{du}=\left(\ln{\left(x \right)}\right)^{\prime }dx=\frac{dx}{x}$$$ (步骤见 »)，并且 $$$\operatorname{v}=\int{\frac{1}{x^{6}} d x}=- \frac{1}{5 x^{5}}$$$ (步骤见 »)。

因此，

$${\color{red}{\int{\frac{\ln{\left(x \right)}}{x^{6}} d x}}}={\color{red}{\left(\ln{\left(x \right)} \cdot \left(- \frac{1}{5 x^{5}}\right)-\int{\left(- \frac{1}{5 x^{5}}\right) \cdot \frac{1}{x} d x}\right)}}={\color{red}{\left(- \int{\left(- \frac{1}{5 x^{6}}\right)d x} - \frac{\ln{\left(x \right)}}{5 x^{5}}\right)}}$$

对 $$$c=- \frac{1}{5}$$$ 和 $$$f{\left(x \right)} = \frac{1}{x^{6}}$$$ 应用常数倍法则 $$$\int c f{\left(x \right)}\, dx = c \int f{\left(x \right)}\, dx$$$：

$$- {\color{red}{\int{\left(- \frac{1}{5 x^{6}}\right)d x}}} - \frac{\ln{\left(x \right)}}{5 x^{5}} = - {\color{red}{\left(- \frac{\int{\frac{1}{x^{6}} d x}}{5}\right)}} - \frac{\ln{\left(x \right)}}{5 x^{5}}$$

应用幂法则 $$$\int x^{n}\, dx = \frac{x^{n + 1}}{n + 1}$$$ $$$\left(n \neq -1 \right)$$$，其中 $$$n=-6$$$：

$$\frac{{\color{red}{\int{\frac{1}{x^{6}} d x}}}}{5} - \frac{\ln{\left(x \right)}}{5 x^{5}}=\frac{{\color{red}{\int{x^{-6} d x}}}}{5} - \frac{\ln{\left(x \right)}}{5 x^{5}}=\frac{{\color{red}{\frac{x^{-6 + 1}}{-6 + 1}}}}{5} - \frac{\ln{\left(x \right)}}{5 x^{5}}=\frac{{\color{red}{\left(- \frac{x^{-5}}{5}\right)}}}{5} - \frac{\ln{\left(x \right)}}{5 x^{5}}=\frac{{\color{red}{\left(- \frac{1}{5 x^{5}}\right)}}}{5} - \frac{\ln{\left(x \right)}}{5 x^{5}}$$

因此，

$$\int{\frac{\ln{\left(x \right)}}{x^{6}} d x} = - \frac{\ln{\left(x \right)}}{5 x^{5}} - \frac{1}{25 x^{5}}$$

化简：

$$\int{\frac{\ln{\left(x \right)}}{x^{6}} d x} = \frac{- 5 \ln{\left(x \right)} - 1}{25 x^{5}}$$

加上积分常数：

$$\int{\frac{\ln{\left(x \right)}}{x^{6}} d x} = \frac{- 5 \ln{\left(x \right)} - 1}{25 x^{5}}+C$$

$$$\int \frac{\ln\left(x\right)}{x^{6}}\, dx = \frac{- 5 \ln\left(x\right) - 1}{25 x^{5}} + C$$$A