Integral of $$$18 u$$$

Find $$$\int 18 u\, du$$$.

Apply the constant multiple rule $$$\int c f{\left(u \right)}\, du = c \int f{\left(u \right)}\, du$$$ with $$$c=18$$$ and $$$f{\left(u \right)} = u$$$:

$${\color{red}{\int{18 u d u}}} = {\color{red}{\left(18 \int{u d u}\right)}}$$

Apply the power rule $$$\int u^{n}\, du = \frac{u^{n + 1}}{n + 1}$$$ $$$\left(n \neq -1 \right)$$$ with $$$n=1$$$:

$$18 {\color{red}{\int{u d u}}}=18 {\color{red}{\frac{u^{1 + 1}}{1 + 1}}}=18 {\color{red}{\left(\frac{u^{2}}{2}\right)}}$$

Therefore,

$$\int{18 u d u} = 9 u^{2}$$

Add the constant of integration:

$$\int{18 u d u} = 9 u^{2}+C$$

$$$\int 18 u\, du = 9 u^{2} + C$$$A