integral of 4/sqrt(x^2)

$$\int {\frac{ 4 }{ \sqrt{ x^2 } } \ dx } =4*\int { \frac{ 1 }{ x } \ dx }\\ we \ substitute \ x=e^u \ then \ \ dx=e^u \ du\\ we \ have \ 4* \int { \frac{ e^u }{ e^u } \ du }=4*\int{ \ du }=4*u\\ u=\ln{ x} \\ solution: \ \ 4*\ln{ (x)}+c$$