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设函数f(x)可导,且f(0)=0,F(x)=∫x0tn-1f(xn-tn)dt,求limx→0F(x)x2n.

题目详情
设函数f(x)可导,且f(0)=0,F(x)=
x
0
tn-1f(xn-tn)dt,求
lim
x→0
F(x)
x2n
▼优质解答
答案和解析

∵F(x)=
x
0
tn−1f(xn−tn)dt=
1
n
x
0
f(xn−tn)d(xn−tn),
令:u=xn-tn,则:
F(x)=−
1
n
0
xn
f(u)du=
1
n
xn
0
f(u)du,
lim
x→0
F(x)
x2n
=
lim
x→0
1
n
xn
0
f(u)du
x2n

=
1
n
lim
x→0
nxn−1f(xn)
2nx2n−1

=
1
2n
lim
x→0
f(xn)
xn

=
1
2n
lim
x→0
f(xn)−f(0)
xn

=
f′(0)
2n