f'(x)=1/x-1/e=0得x=e,当0＜x＜e时,f'(x)＞0；当x＞e时,f'(x)＜0；所以函数先递增再递减,那么f(x)在x=e处取到极大值和最大值,为k；当x趋于0时和趋于正无穷大时,f(x)都趋于负的无穷大；当k＜0时,f(x)在区间(0,正无穷)...