When h approaches 0, Lim H / F (A-H) - f (a) = 1 / 3, then the derivative of F (a) is

When h approaches 0, Lim H / F (A-H) - f (a) = 1 / 3, then the derivative of F (a) is

lim(h->0) h/[f(a-h)-f(a)]=1/3
lim(h->0) [f(a-h)-f(a)] /h=3
-lim(h->0) [f(a) -f(a-h)] /h=3
-f'(a) =3
f'(a) =-3