Answer:
64.
Explanation:
We have been given an equation
. We are asked to complete the square for the given equation.
We know that to complete a square, we add half the square of x term to both sides of equation to complete square.
We can see that coefficient of x term is 16.

Add 64 on both sides of equation:



Therefore, 64 needs to be added to both sides of the equation in order to complete the square.