Algebra 1 · Quadratic Functions
Completing the Square
Algebra 1 · Quadratic Functions
Definition
Completing the square is a method that rewrites a quadratic as a perfect square plus a constant.
Teach it
Where it is taught, with guided notes, practice, homework, an exit ticket and an interactive Teacher Deck.
Examples
- x2 + 6x = (x + 3)2 − 9.
- x2 − 4x + 1 = (x − 2)2 − 3.
Key rule
Add and subtract (b/2)2 to form a perfect square.
Memory hook
Complete the square − add (b/2)2 to build the square.