设连续函数f(x)=ln
,证明:
。
参考答案:由于定积分表示一个数值,可设[*],从而f(x)=ln x-A,将上式两端分别在[1,e]上取定积分,有 [*] 故[*]
Health is important to us. We should have more vegetables and fruit and we shouldn’t eat _____ junk food.
A.too much
B.much too
C.very much
D.very
准轨铁路轨距是()。