选讲里，使用柯西不等式(x+y+z)[x^2/(y+x)+y^2/(x+z)+z^2/(x+y)]≥(x+y+z)^2x,y,z是正实数∴x+y+z>0∴x^2/(y+x)+y^2/(x+z)+z^2/(x+y)≥x+y+z就一步如果你认可我的回答，请点击“采纳回答”，祝学习进步！
