f(x)=(x-3)/(x+3)求导
问题描述：
f(x)=(x-3)/(x+3)求导
答
f =(x-3)/(x+3)
f '=[(x-3)' (x+3)-(x-3)(x+3)']/(x+3)^2
=[(x+3)-(x-3)]/(x+3)^2
=6/(x+3)^2