MCQ
If $a_1, a_2...,a_n$ an are positive real numbers whose product is a fixed number $c$ , then the minimum value of $a_1 + a_2 +.... + a_{n - 1} + 2a_n$ is
  • $n(2c)^{1/n}$
  • B
    $(n + 1)c^{1/n}$
  • C
    $2nc^{1/n}$
  • D
    $(n + 1)(2c)^{1/n}$

Answer

Correct option: A.
$n(2c)^{1/n}$
a
$\mathrm{A} \cdot \mathrm{M} . \geq \mathrm{G} \cdot \mathrm{M}$

$\Rightarrow \frac{a_{1}+a_{2}+\ldots+a_{n-1}+2 a_{n}}{n} \geq\left(a_{1} \cdot a_{2} \ldots a_{n-1} \cdot 2 a_{n}\right)^{1 / n}$

$\Rightarrow a_{1}+a_{2}+\ldots+2 a_{n} \geq n(2 c)^{1 / n}$

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