Giải thích các bước giải:
$\left ( \dfrac{a}{b} \right )^{2} + \left ( \dfrac{b}{c} \right )^{2} + \left ( \dfrac{c}{a} \right )^{2} \geq \dfrac{a}{b} + \dfrac{b}{c} + \dfrac{c}{a}$
$\Leftrightarrow 2\left ( \dfrac{a}{b} \right )^{2} + 2\left ( \dfrac{b}{c} \right )^{2} + 2\left ( \dfrac{c}{a} \right )^{2} \geq 2\dfrac{a}{b} + 2\dfrac{b}{c} + 2\dfrac{c}{a}$
