The product of (a − b)(a − b) is solved using the perfect square trinomial formula. This formula (for subtraction) states that (a − b)^2 = a^2 - 2ab + b^2.
The first term of the product is always the first term of the original binomial squared.
The middle term of the product is always positive and equal to twice the product of the first and last terms of the original binomial.
The last term of the product is always positive and equal to the last term of the original binomial squared.
a^2 - 2ab + b^2 is NOT equal to a^2 − b^2.
So, the product of (a − b)(a − b) is NEVER a2 − b2
