Polynomials in the form of difference of squares can be factored as:

a^2-b^2=(a+b)(a-b)

Select all of the polynomials below that are in the form of difference of squares.
(Select all that apply.)

x^2-9
4x^2-144y^2
y^2+25
9a^2-b^2
100a-64b^2
16-a^2

x^2-9

9a^2-b^2