(1+2x+x2)20 = (1+x)2
so , ((1+x)2)20 = (1+x)40
so from binomial expansion ,we have
40c0 x40 +40c1 x39 .............40c40 x0
so total terms in the expansion will be 41.
(40 terms will be there from 40c1 to 40c40 + 1 term 40c0 so total terms will be 41)