Question
If `2^(n - 1) + 2^(n + 1) `= 320, then n is equal to :
Answer: Option D
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`2^(n - 1) + 2^(n + 1) = 320 hArr 2^(n - 1) (1 + 2^2) = 320 hArr 5 xx 2^(n - 1) = 320`
`hArr 2^(n - 1) = 320/5= 64 = 2^6 hArr n- 1 = 6 hArr n= 7`
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