Question

What number must you add to complete the square? x^2+6x=15

Answer 1

To complete the square you must split the b term in half, then square that answer.

6 is the b term, half of 6 is 3, 3 squared is 9. You will add 9 to both sides of x^2 + 6x = 15

x^2 + 6x + 9 =  24

Answer 2

I believe it would be 3±26