1for Sn=nn-1/(n-1)
(n-1)Sn=nn-1
put n=2,3,......,n and adding(we have to take one more term For S1 which equals n) we get
LHS=n+ summation of kn(k varies from 2 to n)-(n-1)
=1+ summation of kn(k varies from 2 to n)
=RHS
this is the required result!
If S1,S2.....Sn be the sum of first nterms of n G.Ps whose 1st terms of each unity and C.R are 1,2,3.....n respectively
prove
S1+S2+2S3+3S4+.....(n-1)Sn=
1n+2n+3n+.....+nn.
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3 Answers
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