Giải thích các bước giải:
Bài 1:
$(4+\dfrac{a}{b})(9+\dfrac{b}{c})(25+\dfrac{c}{a})\ge 2\sqrt{4.\dfrac{a}{b}}. 2\sqrt{9.\dfrac{b}{c}}. 2\sqrt{25.\dfrac{c}{a}}$
$\rightarrow (4+\dfrac{a}{b})(9+\dfrac{b}{c})(25+\dfrac{c}{a})\ge 240.\sqrt{\dfrac{a}{b}.\dfrac{b}{c}.\dfrac{c}{a}}$
$\rightarrow (4+\dfrac{a}{b})(9+\dfrac{b}{c})(25+\dfrac{c}{a})\ge 240$