You can identify that the expression is a polynomial and its degree is 2.
As you can see in the exercise, it has the following form:
[tex]ax^2+bx^{}+c[/tex]You know two terms of the expression:
[tex]y^2+16y[/tex]By definition, a Perfect square expression is an expression that can be factored in the form of the product of two Binomials:
[tex]\begin{gathered} a^2+2ab+b^2=(a+b)(a+b) \\ \\ a^2-2ab+b^2=(a-b)(a-b) \end{gathered}[/tex]Therefore, knowing the two terms of the expression given, you can set up that:
[tex]\begin{gathered} a=y \\ \\ 2ab=(2)(y)(8)=16y \end{gathered}[/tex]Then:
[tex]b^2=(8)^2=64[/tex]The answer is:
[tex]64[/tex]