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  • Which term of the following sequences: 2 2 2 ^ 1/2 4 is 128

5(a)   Which term of the following sequences:  

                   2,2\sqrt 2 , 4 .,....is \: \: 128 ?

Answers (1)

best_answer

Given :  GP = 2,2\sqrt 2 , 4 .,............

a=2\, \, \, \, \, and \, \, \, \, \, r=\frac{2\sqrt{2}}{2}=\sqrt{2}

n th term is given as 128.

a_n=a.r^{n-1}

\Rightarrow 128=2.(\sqrt{2})^{n-1}

\Rightarrow 64=(\sqrt{2})^{n-1}

\Rightarrow 2^6=(\sqrt{2})^{n-1}

\Rightarrow \sqrt{2}^1^2=(\sqrt{2})^{n-1}

\Rightarrow n-1=12

\Rightarrow n=12+1=13

The, 13 th term is 128.

Posted by

seema garhwal

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