Question

What number must you add to complete the square x^2+4x=5

Answer 1

4

Explanation:

x² + 4x = 5

b = 4

We need to add (b/2)² to both sides to complete the square.

(4/2)² = 4

x² + 4x + 4 = 5 + 4

x² + 4x + 4 = 9

(x + 2)² = 9

Answer 2

You should add 4 to both sides because that would make the left side a perfect square which is what you are intending to do when you complete the square.