6. 5x(x 2 – 4)

9. (y 2 + 4)(y 2 – 4)

10. (9 + d 2 )(9 – d 2 )

13. 3x(x 4 – 4)

14. 5(x 3 + 5x 2 – 9x – 45) 5[(x 3 + 5x 2 ) + (-9x – 45)] 5[x 2 (x + 5) – 9(x + 5)] 5(x + 5)(x 2 – 9)

16. q + 2 / 5 = 0 q = - 2 / 5 q – 2 / 5 = 0 q = 2 / 5 {- 2 / 5, 2 / 5 }

17. m 2 – 81 = 0 (m + 9)(m – 9) = 0 m + 9 = 0m – 9 = 0

21. 9x 2 = (3x) 2 16 = (4) 2 -12x = -2(3x)(4)

22. 49x 2 = (7x) 2 4 = (2) 2 28x = 2(7x)(2)

25. 3(x 2 – 1)

26. 2(2x 2 + 5x + 3) b = 5, ac = 6 2(2x 2 + 2x + 3x + 3) 2[2x(x + 1) + 3(x + 1)]

28. 4x 2 + 36x = -81 +81 4x 2 + 36x + 81 = 0 (2x + 9) 2 = 0 2x + 9 = 0 2x = -9 x = -9 / 2

29. (3x – 5) 2 = 0 3x – 5 = 0 3x = 5

30. x 2 – 16 = 0Original Equation Add 16 to each side. x 2 = 16 Take the square root of each side.

32. b – 7 = 6b – 7 = -6 b = 13b = 1 {13, 1}

33. x – 4 = ±5 x – 4 = 5x – 4 = -5

35. -5 = -16t 2 Throw out the negative. t = 0.56 seconds

36. 0 = -16t 2 + 10 -10 = -16t 2 Throw out the negative.