b1:choa;b;c>0.CMR\(\frac{a}{b}\)+\(\frac{b}{c}\)+\(\frac{c}{a}\)\(\ge\)\(\frac{a+b}{b+c}\)+\(\frac{b+c}{a+b}\)+1
b2:cho x;y;z>1 tm \(\frac{1}{x}\)+\(\frac{1}{y}\)+\(\frac{1}{z}\)=2.CMR\(\sqrt{x+y+z}\)\(\ge\)\(\sqrt{x-1}\)+\(\sqrt{y-1}\)+\(\sqrt{z-1}\)
b3:cho x;y;z>0 tm x+y+z=xyz.CMR \(\frac{1}{\sqrt{1+x^2}}\)+\(\frac{1}{\sqrt{1+y^2}}\)+\(\frac{1}{\sqrt{1+Z^2}}\)\(\le\)\(\frac{3}{2}\)