If the n^{th} term of the G.P. 2,2\sqrt{2},4,...... is 128 then n=

AP ICET 2015 Paper

Question : 129 of 200

Marks: +1, -0

If the

n^{th}

term of the G.P.

2,2√{2},4,......

is 128 then

n=

Solution:

Given

a=2,r=√2=2^{1/2}

nth term of G.P.

=ar^{n–1}=2(2^{1/2})^{n-1}

⇒2^{{n-1}/2}=128/2=64=2^6

⇒{n-1}/2=6

⇒n=(6×2)+1=13

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