MCQ
The minimum value of the expression $3^x+3^{1-x}$, $x \in R$, is
  • A
    $0$
  • B
    $\frac{1}{3}$
  • C
    3
  • $2 \sqrt{3}$

Answer

Correct option: D.
$2 \sqrt{3}$
(D) $2 \sqrt{3}$
Explanation : We know that, A.M. $\geq$ G.M. for positive numbers.
$
\begin{array}{ll}
\text { Therefore, } & \frac{3^x+3^{1-x}}{2} \geq \sqrt{3^x \cdot 3^{1-x}} \\
\Rightarrow & \frac{3^x+3^{1-x}}{2} \geq \sqrt{3^x \cdot \frac{3}{3^x}} \\
\Rightarrow & 3^x+3^{1-x} \geq 2 \sqrt{3}
\end{array}
$

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