The constant term in the expansion of (x2-1x2)16 is
(1)
Let (r+1)th term be the constant term in the expansion of (x2-1x2)16
∴ Tr+1=Cr16x2r(-1x2)16-r
=(-1)16-r Cr16x2r·x-32+2r=(-1)16-r Cr16x4r-32
For constant term, 4r-32=0⇒r=8
∴ T9=(-1)8 C816=C816