\int(2x+ \sqrt{3x+1})dx=x^{2}+ \int \sqrt{3x+1}dx= / t= \sqrt{3x+1},dx=\frac{2}{3}tdt/=x^{2}+\frac{2}{3} \int t^{2}dt=x^{2}+ \frac{2}{9}t^{3}=x^{2}+ \frac{2}{9}(3x+1)^{\frac{3}{2}}