∫2x(x2+1)3 dx=\displaystyle\int 2x(x^2 + 1)^3\,dx =∫2x(x2+1)3dx=A(x2+1)4+C(x^2+1)^4 + C(x2+1)4+CBx44+C\dfrac{x^4}{4} + C4x4+CC(x2+1)33+C\dfrac{(x^2+1)^3}{3} + C3(x2+1)3+CD(x2+1)44+C\dfrac{(x^2+1)^4}{4} + C4(x2+1)4+Ccheck_circleExplanationu=x2+1u = x^2 + 1u=x2+1, du=2x dxdu = 2x\,dxdu=2xdx. ∫u3 du=u4/4\int u^3\,du = u^4/4∫u3du=u4/4.