What’s the missing constant of x^2+6x

Question

What’s the missing constant term in the perfect square that starts with x^2+6x

Answer 1

x^2 + 6x + 9

take half the coefficient of x and square it

(6/2)^2 = 3^2 = 9 = the missing constant

x^2 +6x + 9 = (x+3)^2