A) 1/3
B) 3/2
C) 3/4
D) 2/3
Correct Answer: D
Solution :
Infinite series is \[a,\ ar,\ a{{r}^{2}}........\infty \] Sum \[S=\frac{a}{1-r}=9\Rightarrow a=9(1-r)\] ?..(i) and \[a+ar=5\] \[\Rightarrow a(1+r)=5\Rightarrow 9(1-r)(1+r)=5\] [By equation (i)] \[\frac{{{2}^{n}}-1}{{{2}^{n-1}}}=\frac{255}{128}\].
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