If using the method of completing the square to solve the quadratic equation x^2+8x-4=0 which number would have to be added to "complete the square"? I need the answer ASAP. Please help. Thank you

x^2 + 8x - 4 = 0

(x^2 + 8x + 8/2^2) - 4 - 8/2^2 = 0

(x^2 + 8x + 16) - 4 - 16 = 0

(x^2 + 8x + 16) - 20 = 0

(x + 4)(x + 4) - 20 = 0

The number that is to be added to complete the square is 8/2^2, or 16.

unless if u could do my questions, if not i wouldn't want to