$\frac{d v}{d x}=x$
\(v = \frac{1}{2}x^2 + C\)
Step 1 :\(\frac{d v}{d x}=x\)
Step 2 :\(\int \frac{d v}{d x} dx = \int x dx\)
Step 3 :\(v = \frac{1}{2}x^2 + C\)