Could some one help breaking the steps for finding the diffenrece quotient?

Questions
1

f(x+h)-f(x) over h

for f(x) =( 6-4x)/x

Thanks In Advance

2

ClearAll[f, x, h]
f[x_] := (6 - 4 x)/x;
r = (f[x + h] - f)/h;
r = Simplify[r]

It gives -(6/(h x + x^2)) You can verify this result as follow

  Simplify[D[f[x], x] - Limit[r, h -> 0]]
  (* 0 *)