Algebra I Recipe: Solving Quadratic Equations By Completing the Square
By G Redden
- Add or subtract to move the number term to the opposite side of x2 and x.
- If "a" > 1, divide both sides by "a". (Divide every term by "a".)
- Take half of "b", square it and add the value to both sides of the equation.
- Factor the perfect square trinomial on the left. Factors to look like (a ± b)2.
- Square root both sides of the equation to eliminate the "2". Give the positive and negative value of the right side.
- Solve for the variable.
1.
x2 + 10x – 11 = 0
2.
x2 - 8x + 12 = 0
3.
2x2 - 6x - 15 = 5
4.
5x2 - 20x – 20 = 5