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shivusuja

Member

Registered: 2006-09-14

Posts: 56

sequences and series

please help me out of this problem

find the ratio of the sum of first n terms of a G.P to the sum of terms from (n+1)th to (2n)th term.

Jai Ganesh

Administrator

Registered: 2005-06-28

Posts: 46,190

Re: sequences and series

The sum of n terms of the GP is a(r^n-1)/(r-1).....(1)
The sum of 2n terms is a(r^2n-1)/(r-1).
The sum of (n+1) terms is a(r^n)/(r-1).
The sum of terms from (n+1) to 2n is
a/(r-1)[r^(2n-1)-r^(n)]......(2)
The ratio is (1)/(2)=[r^(n-1)]/[r^(2n-1)-r^(n)]
(ASSUMING THAT r>1.)

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