Interactive Mathematics by Kunio Mitsuma, Ph.D.

Question: How do we find the difference quotient of f (x) = 4x² – 2x?

Yours Truly answers: When we use the formula

to compute the difference quotient, the correct steps should look like this:

When mistakes are made, they usually occur with sign changes in the 2nd line and factorization of h in the last step. See that when we factor h out of 2h, the 2 still survives.