Watch the video below to see how to solve a quadratic equation by completing the square.

Practice: Solve x² − 20x = -51 by completing the square.

Move each rectangle to show the correct order in solving a quadratic equation by completing the square.

The solutions for the equation x² − 20x = -51 are x = 17 and 3.

Your turn: On your own paper, solve the quadratic equation given below by completing the square.

Click on the hints for help, the solution for the answer, and the detailed solution to explain the steps.

x2 + 12x − 28 = 0

Interactive popup. Assistance may be required. Hint 1 Add 28 to both sides of the equation so that only the x terms are on the left side of the equation.

Interactive popup. Assistance may be required. Hint 2 You will need to add 36 to both sides of the equation since 1 2 (12)= 6 and 62 = 36

Interactive popup. Assistance may be required. Hint 3 Be sure to use ± before you take the square root of the right side of the equation.

Interactive popup. Assistance may be required. Solution x = –14 and x = 2

Interactive popup. Assistance may be required. Detailed Solution