Answer:
(x +4)^2 -45
Explanation:
The square of a binomial has the form ...
(x +a)^2 = x^2 +2ax +a^2
That is, the constant term (a^2) is the square of half the coefficient of the linear term: (2a/2)^2 = a^2.
To "complete the square", you add 0 in the form of the desired constant added to its opposite. Here, we want the constant for the square to be (8/2)^2 = 16. So, we can add 0 = 16 -16 to the expression:
x^2 +8x +16 -29 -16
(x^2 +8x +16) -45 . . . . group the terms that make the square
(x +4)^2 -45 . . . . rewritten after completing the square