A) \[6\]
B) \[8\]
C) \[5\]
D) \[7\]
Correct Answer: D
Solution :
\[{{2}^{x-1}}+{{2}^{x+1}}=320\] \[\Rightarrow \]\[{{2}^{x-1}}\left( 1+{{2}^{2}} \right)=320\] \[\Rightarrow \]\[{{2}^{x-1}}\times 5=320\] \[\Rightarrow \]\[{{2}^{x-1}}=\frac{320}{5}=64\Rightarrow {{2}^{x-1}}={{2}^{6}}\] \[\Rightarrow \]\[x-1=6\Rightarrow x=7\]
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