The purpose of this lesson is for students to reason from the meaning of a square and the meaning of a square root to solve equations of the form and , where is positive. They use graphs to understand that positive numbers always have two square roots, one positive and one negative. They also consider why we might want to represent a single value rather than both values that square to make . Then they use graphs to understand why equations like have only one solution. There is no focus on equation-solving procedures in this lesson, which is something students will turn their attention to and develop techniques regarding in later lessons.

Note that there are certain claims like, “The equation has no solution,” which would be more precisely stated as “The equation has no real solution.” However, students don’t know about any numbers other than real numbers, so it does not make sense to make this distinction at this time.

Students attend to precision when they reason about solutions to equations involving squares and square roots from the meaning of the symbol (MP6).