Let f x 4 x 8 f x lim h 0 Your answer above and the next few answers below will involve the variables h and z The expression inside the limit simplifies to a simple fraction with Numerator Then according to the definition of derivative Denominator NOTE Both of the previous two parts must be correct in order to receive partial credit We can cancel the factor appearing in the denominator against a similar factor appearing in the numerator leaving a simpler fraction with Numerator Denominator NOTE All three of the previous parts must be correct to receive partial credit Taking the limit of this fractional expression as h 0 gives us f x