Calculus (3rd Edition)

$$\int \frac{ d x}{x+7} =\ln |x+7|+C$$
Recall that $\int \frac{1}{x}dx=\ln |x|+C$ Le $u=x+7$ and hence $du=dx$, then we have $$\int \frac{ d x}{x+7}=\int \frac{ d u}{u}= \ln |u|+c=\ln |x+7|+C.$$