(1) f'(1)=1 - m =0 ;则 m=1
(2)将m=1代入 f'(x) 有 f'(x) = x + a/x - (a + 1),
求函数f(x)的单调增区间,即f'(x) = x + a/x - (a + 1) >=0
若 x>0;
(x-a)(x-1)>=0 ,当a>=1时,x>=a 或xa 或0