![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
![](https://blog.hocmai.vn/wp-content/uploads/2017/07/hot.gif)
Cho các số thực a,b,c thỏa mãn [tex]0\leqslant a,b,c\leqslant 1[/tex] và [tex]\dpi{100} \fn_jvn a+b+c\geqslant 2[/tex].CMR:
[tex]\dpi{100} \fn_jvn $ab(a+1)+bc(b+1)+ca(c+1)\geqslant 2$[/tex]
[tex]\dpi{100} \fn_jvn $ab(a+1)+bc(b+1)+ca(c+1)\geqslant 2$[/tex]