In this lesson, students examine some identities that are useful for expressions that include square roots. First, students take the two zeros guaranteed by the quadratic formula and use them to reconstruct the standard form of a quadratic expression. Then students use the difference of squares identity, , to remove the root from the denominator of a rational expression. Finally, students use the identities they have learned in this lesson to use two -intercepts and a third point on the parabola to write a quadratic function. Throughout the lesson, students must use the structure of the expressions to rewrite expressions in another form (MP7).