Question

Express 9-y^2 as the product of two binomial factors.

Answer 1

3^2-y^2

then apply formula (a-b)(a+b)=a^2-b^2

so,,
(3-y)(3+y)

Answer 2

Recognize the difference of 2 perfect squares
remember that
a²-b²=(a-b)(a+b)
so
9=3²
y²=y²

9-y²=
3²-y²=
(3-y)(3+y)