Answer:
9
Explanation:
The given equation is:
 - 6
 = 5
To complete the square you have to add one number to both sides of the equation. 
First, divide the coefficient of the term x by 2 and square the result. This number should then be added to both sides of the equation.
For the equation 
 - 6
 = 5 the coefficient of the term x is -6.
(6 ÷ 2)² = 9
So you'll add 9 to both sides of the equation.
 
 - 6
 (+ 9) = 5 (+ 9)
 ↓
 
 - 6
 + 9 = 14
This can also be written as:
 (
 - 3)² = 14