The coefficient of the term independent of x in (x2−1x)9 is
1
-1
48
84
Tr+1=9Cr(x2)9−r(−1x)r
= 9Cr(−1)rx18−3r
For term, independent of x,
18 - 3r = 0 ⇒ r = 6
∴ term independent of x = 9C6(−1)6 = 84.