Let (1+x2)2(1+x)n=A0+A1x+A2x2+..............If A0,A1,A2 are in A.P., then the value of n is
2
3
5
7
(1+x2)2(1+x)n = (1+2x2+x4)nC0 + nC1 x+ nC2 x2+..............)
=nC0 +nC1 x+(nC2+2.nC0)x2+......
Hence A0=1;A1=nC1;A2=nC2+2 which are in A.P.