Answer:
[tex]\boxed{x^2 - 6x + 9 - y^2}.[/tex]
Step-by-step explanation:
We start by applying the difference of squares to the expression:
[tex]((x-3)-y)((x-3)+y) = (x-3)^2 - y^2.[/tex]
Now we apply the square of a binomial to the first term:
[tex](x-3)^2 - y^2 = x^2 - 2 \times 3 \times x + 3^2 - y^2 = x^2 - 6x + 9 - y^2.[/tex]
So the answer is:
[tex]\boxed{x^2 - 6x + 9 - y^2}.[/tex]
