1ya.just a little. answer is: 2n+ 3n+.............nn + (n-1)
IF S1,S2,S3,......................,Sn ARE THE SUMS OF n TERMS OF n GP's WHOSE FIRST TERM IS 1 IN EACH CASE AND COMMON RATIO ARE 1,2,3,............n RESPECTIVELY,THEN PROVE THat S1+S2+2S3+3S4+...............+(n-1)Sn=1n+2n+3n+.............................nn
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4 Answers
1i think ur Q is wrong again
Sr = 1 + r + r2 + ... + rn-1 = (rn-1)/(r-1)
for r > 1
S1 = 1
so,
(r-1)Sr = rn-1
S1 + S2 + 2S3 + ... + (n-1)Sn = 1 + 2n - 1 + 3n - 1 + ... nn - 1
= 1n + 2n + 3n + ... nn - (n-1)
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