Answer:
9. 64+16n+n^2
10. x^2-121
11. 40b^2-45b+5
12. x^2+6x+9
Explanation:
9. Use FOIL(multiply first terms in both polynomials, then the outer terms, then the inner terms and finally the last terms adding them together). You get 8^2+8n+8n+n^2, which is 64+16n+n^2.
10. This one is a special equation. If (a-b)(a+b), then the answer will be a^2-b^2. Plug in your values, and you get x^2-121.
11. Use FOIL again, getting 40b^2-45b+5.
12. And FOIL again, getting x^2+6x+9.