设函数f(x)满足f(0)=0,f(0)的导数存在,令F(x)=∫(0~x)t^(n-1)f(x^(n)-t^(n))dt求lim(x-0)F(x)x^(-2n)

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设函数f(x)满足f(0)=0,f(0)的导数存在,令F(x)=∫(0~x)t^(n-1)f(x^(n)-t^(n))dt求lim(x-0)F(x)x^(-2n)

设函数f(x)满足f(0)=0,f(0)的导数存在,令F(x)=∫(0~x)t^(n-1)f(x^(n)-t^(n))dt求lim(x-0)F(x)x^(-2n)
设函数f(x)满足f(0)=0,f(0)的导数存在,令F(x)=∫(0~x)t^(n-1)f(x^(n)-t^(n))dt
求lim(x-0)F(x)x^(-2n)

设函数f(x)满足f(0)=0,f(0)的导数存在,令F(x)=∫(0~x)t^(n-1)f(x^(n)-t^(n))dt求lim(x-0)F(x)x^(-2n)
F'(x)=x^(n-1)f(x^(n)-x^(n))+∫(0~x)t^(n-1)nx^(n-1)f'(x^(n)-t^(n))dt
=nx^(n-1)∫(0~x)t^(n-1)f'(x^(n)-t^(n))dt(因为f(0)=0)
= -x^(n-1)∫(0~x)f'(x^(n)-t^(n))d(x^n-t^n)(因为d(x^n-t^n)= -nt^(n-1)dt)
= -x^(n-1) (f(x^(n)-x^(n))-f(x^(n)-0))(因为∫f'(u)du=f(u))
=x^(n-1) f(x^(n))
因为x趋于0时,x^(2n)、F(x)趋于0,应用罗必达法则:
lim(x-0)F(x)x^(-2n)=lim(x-0)F‘(x)/(2nx^(2n-1))=lim(x-0)f(x^n)/(2nx^n)=f'(0)/(2n)