若0<x2≤1,[x1*(x2^2+1)]/[x2*(x1^2+1)]>1等价于求证x1(x²2+1)>x2(x²1+1)
x1(x²2+1)-x2(x²1+1)=x1x2(x2-x1)+(x1-x2)=(x2-x1)(x1x2-1)≤(x2-x1)(|x1||x2|-1)
<(x2-x1)(x²2-1)≤0
∴[x1*(x2^2+1)]/[x2*(x1^2+1)]>1
若-1≤x2<0,[x1*(x2^2+1)]/[x2*(x1^2+1)]>1等价于求证x1(x²2+1)<x2(x²1+1)
x1(x²2+1)-x2(x²1+1)=x1x2(x2-x1)+(x1-x2)=(x2-x1)(x1x2-1)≤(x2-x1)(|x1||x2|-1)
<(x2-x1)(x²2-1)≤0
∴[x1*(x2^2+1)]/[x2*(x1^2+1)]>1
追问你过程中若若0<x2≤1时,x1(x²2+1)-x2(x²1+1)≤0,则x1(x²2+1)≤x2(x²1+1),求证不对啊。