A) 12
B) 4
C) - 4
D) - 12
Correct Answer: D
Solution :
Let G.P. \[a,\,ar,\,a{{r}^{2}},a{{r}^{3}}\]. Given \[a+\,ar=12\] and\[a{{r}^{2}}+\,a{{r}^{3}}=48\Rightarrow a{{r}^{2}}\left( 1+r \right)=48\]. So\[{{r}^{2}}=4\Rightarrow r=\pm 2r=-2\] , then \[a=-12\]You need to login to perform this action.
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