Cho \(a,b,c\ge0\) và \(a+b+c\le3\)

CMR : \(\dfrac{1}{1+a}+\dfrac{1}{1+b}+\dfrac{1}{1+c}\ge\dfrac{3}{2}\)

Cho a, b, c > 0 và ab + bc + ca = 1.

CMR : \(\dfrac{a^3}{b+c}+\dfrac{b^3}{a+c}+\dfrac{c^3}{a+b}>\dfrac{1}{2}\)

Cho \(a\ge3;a+b\ge5\). CMR : \(a^2+b^2\ge13\)

1+3+5+7+9=25 nha bạn!!!

thế kỉ 18

                                                                                 3+?=2            

                                                                        Ba cộng ?bằng hai

                                                                        Ba cộng má bằng hai!!!