设函数y=f(x)在点x处可导,a,b为常数,且a＞b,则limh→∞ f(x+ah)-f(x-bh)/h =a.f'(x) b.(a+b)f'(x) c.(a-b)f'(x) d.a+b/2 f'(x)应该选那个
问题描述：
设函数y=f(x)在点x处可导,a,b为常数,且a＞b,则limh→∞ f(x+ah)-f(x-bh)/h =
a.f'(x) b.(a+b)f'(x) c.(a-b)f'(x) d.a+b/2 f'(x)
应该选那个
答
limh→∞ f(x+ah)-f(x-bh)/h
={[f(x+ah)-f(x)]+[f(x)-f(x-bh)]}/h
=af'(x)+bf'(x)
=(a+b)f'(x)
选b
今天我回答你多少问题了