1. Cho:
$\left\{\begin{matrix} a,b,c>0 & \\ ab\geq 12, bc\geq 8 & \end{matrix}\right.$
Chứng minh: $A=a+b+c+2(\frac{1}{ab}+\frac{1}{bc}+\frac{1}{ca})+\frac{8}{abc}\geq \frac{121}{2}$
2. cho $a,b,c>0$ và $a=max(a,b,c)$. Tìm min:
$B=\frac{a}{b}+2\sqrt{1+\frac{b}{c}}+3\sqrt[3]{1+\frac{c}{a}}$