This activity is intended to supplement Algebra I, Chapter 10, Lesson 4.
Time required: 40 minutes
Topic: Quadratic Equations
Completing the Square
Perfect Square Trinomials
Teacher Preparation and Notes
The teacher should be prepared to introduce the first problem of the document so students understand the “algebra tile” area representation of a quadratic equation. Teachers could use algebra tiles to introduce the activity if available.
This activity explores completing the square when the coefficient of x2 is one. The teacher should use the pattern recognition by the students to extend the activity to coefficient values other than one after the activity.
To download Cabri Jr. and the calculator file, go to http://www.education.ti.com/calculators/downloads/US/Activities/Detail?id=11750 and select the Cabri Jr Application and SQUARE.8xv. If you already have Cabri Jr. on your calculator, you may still need to download SQUARE
Problem 1 – Introduction
- What is the area of each figure?
- How can the area of the missing square be found?
- How are the side lengths of each figure related?
- How does the factored form relate to the length and width of the completed square?
- How does the quadratic relate to the area of the square?
Problem 2 – Integer Lengths
- How does the coefficient of x in the area equation change each time the width increases by one?
- How is the area of the square or missing square related to the width?
Problem 3 – Non-integer Lengths
- How does the coefficient of x in the Area equation change each time the width increases?
- How is the area of the square in the lower left corner or missing square related to the displayed width?
- How is the coefficient of x related to the length of the square in the lower right corner?
- How is the coefficient of x related to the value of c?
- What is a formula or method for finding the value of c without using the calculator?
Problem 4 – Applying Your Knowledge
In this problem, students will answer questions applying their knowledge for completing the square.
Solutions – student worksheet
- A square of length and width 1 completes the square.
- The coefficient is double the length of the grey square.
- If you take half of the coefficient and square it you get c.
- Add three. Half of 4 squared is 4 and we already have 1 so add three to get 4.