For a function f, let
f*(x)=lim (f(x+h)-f(x-h))/h
h->0
Determine f*(x) for f(x)=(x^2)+x
f(x+h)=(x+h)^2+x+h=x^2+2xh+h^2+x-h
do the same for x-h
then subtract, divide by h.
f*(x)=lim (f(x+h)-f(x-h))/h
h->0
Determine f*(x) for f(x)=(x^2)+x
do the same for x-h
then subtract, divide by h.