T
tiendung_1999
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
1.$\dfrac{1}{a^2+b^2} + \dfrac{1}{ab}$ \geq $\dfrac{6}{(a+b)^2}$
2.$\dfrac{1}{a^2+2b^2+3} + \dfrac{1}{b^2+2c^2+3} + \dfrac{1}{c^2+2a^2+3}$\leq $\dfrac{1}{2}$
2.$\dfrac{1}{a^2+2b^2+3} + \dfrac{1}{b^2+2c^2+3} + \dfrac{1}{c^2+2a^2+3}$\leq $\dfrac{1}{2}$