y'=2xln x-x-1/x - 2应该是y'=2xln x-x-1/x + 2这种解法不简便。(1)先证明 当x>1, (x +1)ln x > x-1,令f(x)= (x +1)ln x - x+1, f'(x)= lnx + 1/x >0 => f(x) > f(1) = 0(2)当x>1,在厅笑上述不等式两边同乘以(x-1)即可证得,(x^2-1)ln x>(x-1)^2(3)当01,由扮弯含(2) 得 ,(1/x^2-1)ln (1/x)>(1/x - 1)^2 变形就可得结论(x=1也成立)