Respuesta :

sqdancefan
Use the power rule
  d(x^n)/dx = n·x^(n-1)
to form the derivative.
  f'(x) = 4·2x -4
  f'(x) = 8x - 4

Now, substitute "a" for "x" to find f'(a):
  f'(a) = 8a - 4