The purpose of the lesson is to familiarize students with the processes for completing the square and steps for proving the quadratic formula. In the associated Algebra 1 lesson, students prove the quadratic formula by completing the square on the general standard form for a quadratic equation. The work of this lesson supports students by carefully examining steps that will be needed for the proof. Students construct viable arguments and critique the reasoning of others (MP3) as they identify and correct errors made in solving quadratic equations, and when they explain each step that should be taken to solve them.