Solution:
Remember that a perfect square is a number (or expression), that can be expressed as the square of a number (or expression). For example,
[tex]a^2-2ab+b^2[/tex]is a perfect square, because it can be expressed as the square of the following expression:
[tex](a-b)[/tex]that is:
[tex](a-b)^2=a^2-2ab+b^2[/tex]now, in this case, notice that:
[tex](w-4)^2=w^2-2(4)w+4^2[/tex]this is equivalent to:
[tex]=w^2-8w+4^2[/tex]or
[tex]=w^2-8w+16[/tex]thus, we can conclude that the missing space in the expression
[tex]w^2-8w\text{ + \_\_\_\_}[/tex]would be 16.
