What number must you add to complete the square x^2-16=23

For this case we must complete squares:

We add the square of half the coefficient of the term "x",

on both sides of the equation:

According to the perfect square trinomial we have:

Rewriting the expression we have:

relating to or denoting a system of numbers and arithmetic based on the number ten, tenth parts, and powers of ten.

it alot will look like this 4.4

is this part of a question or something