Squaring a binomial creates a perfect square trinomial. A perfect square is created when a value is multiplied times itself [such as 5 x 5 = 25, making 25 a perfect square]. Thus, (a + b)(a + b) = a² + 2ab + b², making the trinomial a² + 2ab + b² a perfect square. Notice the middle term = twice [x • 4], or 2(4x) = 8x.
