PLEASE HELP. NO LINKS. NEED REAL EXPLANATION.

Answer:
Step-by-step explanation:
This is very easy watch
x^2-16x+ __
what do we do to find the blank?
We divide 16 by 2 to get 8
then we take the square of 8
which is 64
so this would be x^2-16x+ 64 = 64
REMEMBER 64 goes to BOTH sides of equation