$$\sum\limits_{cyc} \frac{\sqrt{yz}}{x+ 2\sqrt{yz}}\equiv \sum\limits_{cyc} \frac{bc}{a^{2}+ 2\,bc}= 1- \frac{\left ( ab+ bc+ ca \right )\left ( \sum\limits_{cyc}\left ( ab \right )^{2}- \sum\limits_{cyc}\left ( ab\,.\,bc \right ) \right )}{\left (2\,bc+ a^{2} \right )\left ( 2\,ca+ b^{2} \right )\left ( 2\,ab+ c^{2} \right )}\leqq 1$$
có thể cho minh xin cách trình bày theo cấp 2 đc ko bạn