What number must you add to complete the square x2+12x=40

36

Step-by-step explanation:

Find a value that is equal to the square of half of b, coefficient of x

(b/2) ^2 = (12/2) ^2

(6) ^2

Add (6) ^2 to both sides.

x^2+12x + (6) ^2 = 40 + (6) ^2

x^2+12x+36=40+36

x^2+12x+36 = 76

Factor the perfect trinomial square into (x+6) ^2

(x+6) ^2 = 76

Thus 36 must be added to both sides to complete the square ...