This Instructional Activity is a part of the Lesson 3, Unit 7, Grade 8. Students solve simple equations that require them to find the square root or cube root of a number. This lesson has two options for showing the existence and uniqueness of positive square roots and cube roots. The first option has students explore facts about numbers on a number line, leading to an understanding of the trichotomy law, followed by a discussion of how the law applies to squares of numbers, which should give students a better understanding of what square roots and cube roots are and how they are unique.