Students continue to rewrite quadratic expressions from standard form to factored form, extending the work to include expressions that can be rewritten as products of a sum and a difference, .

Through repeated reasoning, students notice that when we apply the distributive property to multiply a sum and a difference, the product has a negative constant term, but the linear term can be negative or positive (MP8). Students make use of structure as they take this insight to transform quadratic expressions into factored form (MP7). They see that if a quadratic expression in standard form (with coefficient 1 for ) has a negative constant term, one of its factors must have a negative constant term, and the other must have a positive constant term.