Question

X^2-11x-38=0, which number would have to be added to complete the square

Answer 1

The method is based on the simple observation that, while x2+10xis not a perfect square, x2+ 10x+ 25 is. "Completing the square" means putting in the missing 25 that is needed to form the perfect square. Two obvious concerns are "How do you know you need 25? and "How can you just add 25 anyplace you want?" Here are the steps used: