You have the expression x^2+16x. Then, to find the value that completes the square for it, you must apply the following proccedure:
x^2+16x=0
x^2+16x+0=0
This quadratic equation needs to have the following form:
a(x+d)^2+e
Then, you have:
(b/2)^2=(16/2)^2=(8)^2=64
Therefore, the expression is:
x^2+16x+64=64
(x+8)^2=64
The answer is the first option= 64
