f(x)=(x-3)/(x+3)導通

f(x)=(x-3)/(x+3)導通

f=(x-3)/(x+3)
f'=[(x-3)'(x+3)-(x-3)(x+3)']/(x+3)
=[(x+3)-(x-3)]/(x+3)
=6/(x+3)