中一數學///急!!

1. (x+9)(2x-3)
= 2x^2 + 15x - 27

2. (2x+3)(7-4x)
= -8x^2 + 2x + 21

3. 6a(a-3)(a+1)
= 6a(a^2 -2a - 3)
= 6a^3 - 12a^2 - 18a

4. -4(3y-5)(2-y)
= -4(-3y^2 + 11y - 10)
= 12y^2 - 44y + 40

5. -p(-8+2)(4+3p)
= -p(-6)(4+3p)
= 6p(4+3p)
= 24p + 18p^2

6. (8a+b)(4a-5b)
= 23a^2 - 36ab - 5b^2

7. (a+4b)(3c-2d)
= 3ac - 2ad + 12bc - 8bd

8.(4t-u)(2u-7t-5)
= (4t-u)(2u-7t)-5(4t-u)
= -2u^2 + 13ut - 28t^2 - 20t + 5u

9. (a+2b-1)(3a-2b-4)
= (a+2b-1)(3a-2b) - 4(a+2b-1)
= 3a^2 - 2ab + 3ab - 4b^2 - 3a + 2b - 4a - 8b + 4
= 3a^2 - ab - 4b^2 - 7a - 6b + 4

10. -(5a+2b-c)(a+b-4c)
= -(5a^2 + 5ab - 20ac + 2ab + 2b^2 - 8bc - ac - bc + 4c^2)
= -5a^2 - 7ab + 21ac - 2b^2 + 9bc - 4c^2


2011-10-09 21:56:27 補充：
5. -p(-8p+2)(4+3p)
= -p(-24p^2 - 26p + 8)
= 24p^3 + 26p^2 - 8p