5. Cho a, b, c > 0; abc = 1. CM: $\dfrac{a^4b}{a^2 + 1}$ + $\dfrac{b^4c}{b^2 + 1}$ + $\dfrac{c^4a}{c^2 + 1}$ $\ge$ $\dfrac{3}{2}$
6. Cho a, b, c > 0. CM: $\mid$ $\dfrac{a^3 - b^3}{a + b}$ + $\dfrac{b^3 - c^3}{b + c}$ + $\dfrac{c^3 - a^3}{c + a}$ $\mid$ $\le$ $\dfrac{(a - b)^2 + (b - c)^2 + (c - a)^2}{4}$
7. Cho a, b, c > 0. CM: $\dfrac{a}{b}$ + $\dfrac{b}{c}$ + $\dfrac{c}{a}$ $\ge$ $\dfrac{a + c}{b + c}$ + $\dfrac{b + a}{c + a}$ + $\dfrac{c + b}{a + b}$
10. Cho a, b, c > 0, a + b + c = 1. CM: $\dfrac{1}{1 - ab}$ + $\dfrac{1}{1 - bc}$ + $\dfrac{1}{1 - ca}$ $\le$ $\dfrac{27}{8}$
Bài viết đã được chỉnh sửa nội dung bởi ginnycandy: 11-08-2013 - 12:32