V
vuoanh1112


bai 1;1<\frac{a}{a+b}+\frac{b}{b+c}+\frac{c}{c+a}<2
bai2;\frac{1}{a+b-c}+\frac{1}{b+c-a}+\frac{1}{c+a-b}>\frac{1}{ a}+\frac{1}{b}+\frac{1}{c}
bai2;\frac{1}{a+b-c}+\frac{1}{b+c-a}+\frac{1}{c+a-b}>\frac{1}{ a}+\frac{1}{b}+\frac{1}{c}