What number must you add to complete the square x^2+12x=-5
a 12
b 36
c 144
d 6

The general form of a quadratic equation is,

                         Ax² + Bx + C = 0

A, B, and C are all numerical coefficients of the terms in the equation. 

In order to complete the square, we divide all numerical coefficients by 2 and A. Then, square the value of B/2A. Performing this operation for this item,

                         n = (B/2A)²

Substituting the known values,

                         n = (12/2(1))² = 36

Thus, the missing number in this item is 36 and the final expression becomes,

                    x² + 12x + 36 = -5 + 36