设函数f(x)可导,f﹙1﹚=1,且满足lnf﹙x﹚-∫f﹙t﹚dt=0。求f(x)

2025-05-23 15:45:55
推荐回答(2个)
回答1:

lnf﹙x﹚=∫f﹙t﹚dt,两边求导得到f'(x)/f(x)=f(x)即df/dx=f²
df/f²=dx,两边积分∫df/f²=∫dx+C,得到-1/f=x+C,即f(x)=-1/(x+C),将x=1代入求的C=-2
所以f(x)=-1/(x-2)

回答2:

lnf﹙x﹚=∫f﹙t﹚dt
f(x)=[lnf(x)]'=f'(x)/f(x)
df(x)/f^2(x)=dx
-1/f(x)=x+C
f﹙1﹚=1, -1=1+C, C=-2
f(x)=1/(2-x)