# Help!! Geometric progression

posted by Collins

Question(1):A G.P has a common ratio of 2 find the value of 'n' for which the sum 2n terms is 33 times the sum of n??
Question(2):in A G.P the product of the 2nd and the 4thterm is double ,the 5th term and the sum of the first 4 term is 80.find the G.P??

1. Steve

r=2, so you want

a(2^(2n)-1) = 33a(2^n-1)
n=5

ar * ar^3 = 2ar^4
a(r^4-1)/(r-1) = 80

a=2, r=3
GP: 2,6,18,54,162

2. Emmrex

When the 8th term of a G.P is divided by the 3rd term, the result is 32 and the 11th term Of the sequence is 4096. Find the c'mon ratio, the first term and the sequence..

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