$\Leftrightarrow \frac{a+ab^2 + b+ a^2b}{(a+b)^{2}(a+c)(b+c)}\leq \frac{1}{\sqrt{(c+a)(c+b)}}$
$\Leftrightarrow \left (\frac{ab+1}{(a+b)(b+c)(c+a)} \right )^{2}\leq \frac{1}{(c+a)(c+b)}$
$\Leftrightarrow (ab+1)^{2}\leq (a+b)(a+c)(b+a)(b+c)$
$\Leftrightarrow (ab+1)^{2}\leq (a^2+1)(b^2+1)$
Điều này luôn đúng
- Matthew James yêu thích