The coefficient of x−10in⁡x2−1x310, is

Let Tr+1 be the (r+1)th  term in the expansion of x2−1x310Then, Tr+1=10Crx20−5r(−1)rThis will contain x−10, if 20−5r=−10⇒r=6∴    Coefficient of x−10=10C6(−1)6=10C6=210