Find the sum of the GP \((1+x)^{21}+(1+x)^{22}+......(1+x)^{30}
The given sequence is geometrical progression with common ratio (1+x)
(1+x)21+(1+x)22+......(1+x)30=(1+x)21(1+(1+x))+.....(1+x)9)
= (1+x)21((1+x)10−1(1−x)−1)
= (1+x)21((1+x)10−1x)
=((1+x)31−(1+x)21x)