x=t3,v=2t and let I=∫dxx=t2−1t3 On differentiating w.r.t. t, we get dtdx=(t2−1)2(t2−1)(3t2)−t3(2t)⇒dtdx=(t2−1)23t4−3t2−2t4⇒dx=(t2−1)2t4−3t2dt⇒dx=(t2−1)2t2(t2−3)dt⇒I=∫(t2−1t3−t2−13t)1⋅(t2−1)2t2(t2−3)dt=∫t(t2−3)t2−1⋅(t2−1)2t2(t2−3)dt=∫t2−1tdt=21∫t2−12tdt=21log(t2−1)+C