Factor each expression.

3x^2 – 5x – 12 = (3x+4)(x-3)
x^2 -9 = (x-3)^2
8x^3+ 12x^2 - 2x - 3 = (4x^2 - 1)(2x + 3)
12x^2 +16x -3= (6x - 1)(2x + 3)
x^2 + 8x - 9= (x + 9)(x - 1) (I can not see who it can all be positive ;_; )
3(x + y) + a(x + y)=  (3x + 3y) + (ax + ay)

7. 3x² - 5x - 12
    3x² - 9x + 4x - 12
    (3x + 4)(x - 3)

8. x² - 9
    x² + 3x - 3x - 9
   (x - 3)(x + 3)

9. 8x³ + 12x² - 2x - 3
    (8x³ + 12x² - 2x - 3)
    (4x² - 1)(2x + 3)

10. 12x² + 16x - 3
      12x² + 18x - 2x - 3
      (6x - 1)(2x + 3)

11. x² + 8x + 9
      (x² + 9x - x + (-9))
      (x - 1)(x + (-9))

Extra Credit: 3(x + y) + a(x + y)
                     3(x) + 3(y) + a(x) + a(y)
                     3x + 3y + ax + ay
                     3x + ax + 3y + ay
                     (3 + a)x + (3 + a)y