Answer:
49
Step-by-step explanation:
When you look at the square of a binomial, you see ...
(x +a)^2 = x^2 +(2a)x +a^2
The constant value (a^2) is the square of half the x-coefficient.
(14/2)^2 = 49 . . . . the value to be added.
Adding 49 gives ...
x^2 +14x +49 = (x +7)^2
