Integral of $$$\ln\left(x^{7}\right) - \ln\left(y^{3}\right)$$$ with respect to $$$x$$$

Find $$$\int \left(7 \ln\left(x\right) - 3 \ln\left(y\right)\right)\, dx$$$.

The input is rewritten: $$$\int{\left(\ln{\left(x^{7} \right)} - \ln{\left(y^{3} \right)}\right)d x}=\int{\left(7 \ln{\left(x \right)} - 3 \ln{\left(y \right)}\right)d x}$$$.

Integrate term by term:

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

Apply the constant rule $$$\int c\, dx = c x$$$ with $$$c=3 \ln{\left(y \right)}$$$:

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

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

$$- 3 x \ln{\left(y \right)} + {\color{red}{\int{7 \ln{\left(x \right)} d x}}} = - 3 x \ln{\left(y \right)} + {\color{red}{\left(7 \int{\ln{\left(x \right)} d x}\right)}}$$

For the integral $$$\int{\ln{\left(x \right)} d x}$$$, use integration by parts $$$\int \operatorname{u} \operatorname{dv} = \operatorname{u}\operatorname{v} - \int \operatorname{v} \operatorname{du}$$$.

Let $$$\operatorname{u}=\ln{\left(x \right)}$$$ and $$$\operatorname{dv}=dx$$$.

Then $$$\operatorname{du}=\left(\ln{\left(x \right)}\right)^{\prime }dx=\frac{dx}{x}$$$ (steps can be seen ») and $$$\operatorname{v}=\int{1 d x}=x$$$ (steps can be seen »).

Thus,

$$- 3 x \ln{\left(y \right)} + 7 {\color{red}{\int{\ln{\left(x \right)} d x}}}=- 3 x \ln{\left(y \right)} + 7 {\color{red}{\left(\ln{\left(x \right)} \cdot x-\int{x \cdot \frac{1}{x} d x}\right)}}=- 3 x \ln{\left(y \right)} + 7 {\color{red}{\left(x \ln{\left(x \right)} - \int{1 d x}\right)}}$$

Apply the constant rule $$$\int c\, dx = c x$$$ with $$$c=1$$$:

$$7 x \ln{\left(x \right)} - 3 x \ln{\left(y \right)} - 7 {\color{red}{\int{1 d x}}} = 7 x \ln{\left(x \right)} - 3 x \ln{\left(y \right)} - 7 {\color{red}{x}}$$

Therefore,

$$\int{\left(7 \ln{\left(x \right)} - 3 \ln{\left(y \right)}\right)d x} = 7 x \ln{\left(x \right)} - 3 x \ln{\left(y \right)} - 7 x$$

Simplify:

$$\int{\left(7 \ln{\left(x \right)} - 3 \ln{\left(y \right)}\right)d x} = x \left(7 \ln{\left(x \right)} - 3 \ln{\left(y \right)} - 7\right)$$

Add the constant of integration:

$$\int{\left(7 \ln{\left(x \right)} - 3 \ln{\left(y \right)}\right)d x} = x \left(7 \ln{\left(x \right)} - 3 \ln{\left(y \right)} - 7\right)+C$$

$$$\int \left(7 \ln\left(x\right) - 3 \ln\left(y\right)\right)\, dx = x \left(7 \ln\left(x\right) - 3 \ln\left(y\right) - 7\right) + C$$$A