Question
Question: If log 2, \(\log(2^{n} - 1)\) and \(\log(2^{n} + 3)\) are in A.P., then *n* =...
If log 2, log(2n−1) and log(2n+3) are in A.P., then n =
A
5/2
B
log25
C
log35
D
23
Answer
log25
Explanation
Solution
As, log 2, log(2n−1) and log(2n+3) are in A.P. Therefore
2log(2n−1)=log2+log(2n+3) ⇒ (2n−5)(2n+1)=0
As 2n cannot be negative, hence 2n−5=0 ⇒ 2n=5 or
n=log25