Solve this following

Question:

Let $f: \mathrm{R} \rightarrow \mathrm{R}$ be such that for all

$x \in R\left(2^{1+x}+2^{1-x}\right), f(x)$ and $\left(3^{x}+3^{-x}\right)$ are in A.P., then the minimum value of $f(x)$ is

 

  1. 0

  2. 3

  3. 2

  4. 4


Correct Option: , 2

Solution:

$f(x)=\frac{2\left(2^{x}+2^{-x}\right)+\left(3^{x}+3^{-x}\right)}{2} \geq 3$

(A.M $\geq$ G.M)

 

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