$$$\frac{\left(3 x + 1\right)^{2}}{244}$$$ 的積分
您的輸入
求$$$\int \frac{\left(3 x + 1\right)^{2}}{244}\, dx$$$。
解答
套用常數倍法則 $$$\int c f{\left(x \right)}\, dx = c \int f{\left(x \right)}\, dx$$$，使用 $$$c=\frac{1}{244}$$$ 與 $$$f{\left(x \right)} = \left(3 x + 1\right)^{2}$$$：
$${\color{red}{\int{\frac{\left(3 x + 1\right)^{2}}{244} d x}}} = {\color{red}{\left(\frac{\int{\left(3 x + 1\right)^{2} d x}}{244}\right)}}$$
令 $$$u=3 x + 1$$$。
則 $$$du=\left(3 x + 1\right)^{\prime }dx = 3 dx$$$ (步驟見»)，並可得 $$$dx = \frac{du}{3}$$$。
該積分變為
$$\frac{{\color{red}{\int{\left(3 x + 1\right)^{2} d x}}}}{244} = \frac{{\color{red}{\int{\frac{u^{2}}{3} d u}}}}{244}$$
套用常數倍法則 $$$\int c f{\left(u \right)}\, du = c \int f{\left(u \right)}\, du$$$，使用 $$$c=\frac{1}{3}$$$ 與 $$$f{\left(u \right)} = u^{2}$$$：
$$\frac{{\color{red}{\int{\frac{u^{2}}{3} d u}}}}{244} = \frac{{\color{red}{\left(\frac{\int{u^{2} d u}}{3}\right)}}}{244}$$
套用冪次法則 $$$\int u^{n}\, du = \frac{u^{n + 1}}{n + 1}$$$ $$$\left(n \neq -1 \right)$$$，以 $$$n=2$$$：
$$\frac{{\color{red}{\int{u^{2} d u}}}}{732}=\frac{{\color{red}{\frac{u^{1 + 2}}{1 + 2}}}}{732}=\frac{{\color{red}{\left(\frac{u^{3}}{3}\right)}}}{732}$$
回顧一下 $$$u=3 x + 1$$$：
$$\frac{{\color{red}{u}}^{3}}{2196} = \frac{{\color{red}{\left(3 x + 1\right)}}^{3}}{2196}$$
因此，
$$\int{\frac{\left(3 x + 1\right)^{2}}{244} d x} = \frac{\left(3 x + 1\right)^{3}}{2196}$$
加上積分常數：
$$\int{\frac{\left(3 x + 1\right)^{2}}{244} d x} = \frac{\left(3 x + 1\right)^{3}}{2196}+C$$
答案
$$$\int \frac{\left(3 x + 1\right)^{2}}{244}\, dx = \frac{\left(3 x + 1\right)^{3}}{2196} + C$$$A