2 votes 2 votes what is the summation of this series? S=nC0*20+nC1*21+nC2*22+..............nCn*2n Combinatory summation + – firki lama asked Jan 17, 2017 • retagged Jun 23, 2017 by Arjun firki lama 439 views answer comment Share Follow See all 2 Comments See all 2 2 Comments reply air1 commented Jan 17, 2017 reply Follow Share $(1+2)^n = \binom{n}{0}1^n2^0 + \binom{n}{1}1^{n-1}2^1 + ... \binom{n}{n}1^02^n$ 8 votes 8 votes firki lama commented Jan 17, 2017 reply Follow Share @air1 thanks...u have solved gate 1987 question this way https://gateoverflow.in/82446/gate1987-9e 0 votes 0 votes Please log in or register to add a comment.