f(x+h)-f(x) over h
for f(x) =( 6-4x)/x
Thanks In Advance
ClearAll[f, x, h] f[x_] := (6 - 4 x)/x; r = (f[x + h] - f[x])/h; r = Simplify[r]
It gives -(6/(h x + x^2)) You can verify this result as follow
-(6/(h x + x^2))
Simplify[D[f[x], x] - Limit[r, h -> 0]] (* 0 *)
