Limit [ (lnx-x/e) / x ,x->+∞ ]= Limit [ (e lnx-x) /(ex) ,x->+∞ ]= Limit [ (e/x - 1) / e ,x->+∞ ] = -1/e当x->+∞ 时,lnx-x/e 与 x 是同阶的无穷大量,Limit [ lnx-x/e ,x->+∞ ] = - ∞