$$$- 2 x + 3 \cos{\left(x \right)} + \frac{1}{x}$$$ 的积分
您的输入
求$$$\int \left(- 2 x + 3 \cos{\left(x \right)} + \frac{1}{x}\right)\, dx$$$。
解答
逐项积分：
$${\color{red}{\int{\left(- 2 x + 3 \cos{\left(x \right)} + \frac{1}{x}\right)d x}}} = {\color{red}{\left(\int{\frac{1}{x} d x} - \int{2 x d x} + \int{3 \cos{\left(x \right)} d x}\right)}}$$
$$$\frac{1}{x}$$$ 的积分为 $$$\int{\frac{1}{x} d x} = \ln{\left(\left|{x}\right| \right)}$$$:
$$- \int{2 x d x} + \int{3 \cos{\left(x \right)} d x} + {\color{red}{\int{\frac{1}{x} d x}}} = - \int{2 x d x} + \int{3 \cos{\left(x \right)} d x} + {\color{red}{\ln{\left(\left|{x}\right| \right)}}}$$
对 $$$c=2$$$ 和 $$$f{\left(x \right)} = x$$$ 应用常数倍法则 $$$\int c f{\left(x \right)}\, dx = c \int f{\left(x \right)}\, dx$$$：
$$\ln{\left(\left|{x}\right| \right)} + \int{3 \cos{\left(x \right)} d x} - {\color{red}{\int{2 x d x}}} = \ln{\left(\left|{x}\right| \right)} + \int{3 \cos{\left(x \right)} d x} - {\color{red}{\left(2 \int{x d x}\right)}}$$
应用幂法则 $$$\int x^{n}\, dx = \frac{x^{n + 1}}{n + 1}$$$ $$$\left(n \neq -1 \right)$$$，其中 $$$n=1$$$：
$$\ln{\left(\left|{x}\right| \right)} + \int{3 \cos{\left(x \right)} d x} - 2 {\color{red}{\int{x d x}}}=\ln{\left(\left|{x}\right| \right)} + \int{3 \cos{\left(x \right)} d x} - 2 {\color{red}{\frac{x^{1 + 1}}{1 + 1}}}=\ln{\left(\left|{x}\right| \right)} + \int{3 \cos{\left(x \right)} d x} - 2 {\color{red}{\left(\frac{x^{2}}{2}\right)}}$$
对 $$$c=3$$$ 和 $$$f{\left(x \right)} = \cos{\left(x \right)}$$$ 应用常数倍法则 $$$\int c f{\left(x \right)}\, dx = c \int f{\left(x \right)}\, dx$$$：
$$- x^{2} + \ln{\left(\left|{x}\right| \right)} + {\color{red}{\int{3 \cos{\left(x \right)} d x}}} = - x^{2} + \ln{\left(\left|{x}\right| \right)} + {\color{red}{\left(3 \int{\cos{\left(x \right)} d x}\right)}}$$
余弦函数的积分为 $$$\int{\cos{\left(x \right)} d x} = \sin{\left(x \right)}$$$：
$$- x^{2} + \ln{\left(\left|{x}\right| \right)} + 3 {\color{red}{\int{\cos{\left(x \right)} d x}}} = - x^{2} + \ln{\left(\left|{x}\right| \right)} + 3 {\color{red}{\sin{\left(x \right)}}}$$
因此，
$$\int{\left(- 2 x + 3 \cos{\left(x \right)} + \frac{1}{x}\right)d x} = - x^{2} + \ln{\left(\left|{x}\right| \right)} + 3 \sin{\left(x \right)}$$
加上积分常数：
$$\int{\left(- 2 x + 3 \cos{\left(x \right)} + \frac{1}{x}\right)d x} = - x^{2} + \ln{\left(\left|{x}\right| \right)} + 3 \sin{\left(x \right)}+C$$
答案
$$$\int \left(- 2 x + 3 \cos{\left(x \right)} + \frac{1}{x}\right)\, dx = \left(- x^{2} + \ln\left(\left|{x}\right|\right) + 3 \sin{\left(x \right)}\right) + C$$$A