Now, we just square the second term of the binomial to get the last term of the perfect square trinomial, so we square three to get the last term, nine. When we add a term to one side of the equation ...Now, we just square the second term of the binomial to get the last term of the perfect square trinomial, so we square three to get the last term, nine. When we add a term to one side of the equation to make a perfect square trinomial, we must also add the same term to the other side of the equation. The process of completing the square works best when the leading coefficient is one, so the left side of the equation is of the form x2+bx+c.
