f(x)=3x/(x^2-1)
f`(x)=(3(x^2-1)-3x*2x)/(x^2-1)^2=(3x^2-6x^2-3)/(x^2-1)^2=(-3x^2-3)/(x^2-1)^2=
= -3(x^2+1)/(x^2-1)^2
f`(0)=-3/1=-3
f`(-2)=-3(4+1)/(4-1)^2=-15/9=-5/3
f(x)=3x/(x^2-1)
f`(x)=(3(x^2-1)-3x*2x)/(x^2-1)^2=(3x^2-6x^2-3)/(x^2-1)^2=(-3x^2-3)/(x^2-1)^2=
= -3(x^2+1)/(x^2-1)^2
f`(0)=-3/1=-3
f`(-2)=-3(4+1)/(4-1)^2=-15/9=-5/3