F.2數學 6題~急~即刻,詳細列式~~ 20點

12a) 2(-q-4)^2
= 2(q^2+8q+16)
= 2q^2+16q+32
16b) (-4(-1-3rs))^2
= 16(1+6rs+9r^2s^2)
= 144r^2s^2 + 96rs + 16
8c) -2(x-y)x-9(x-y)y
= (x-y)(-2x-9y)
= -(x-y)(2x+9y)
9b) -(s-t)-(s-t)^2
= -(s-t)(1+s-t)
9c) 12(p+q)^2－16(p+q)
= (p+q)(12p+12q-16)
11) given that 2x^2＋3x－4=16,find the value of -10x-15x
2x^2+3x-4=16
2x^2+3x-20=0
(2x-5)(x+4)=0
x= 2.5 or x = -4

-10x-15x = -25x

-25x = -25(2.5) = -72.5 or
-25x = -25(-4) = 100

2010-09-19 21:07:43 補充：
-25x = -25(2.5) = -62.5

同埋11題其實係唔係問 -10x^2 -15x??
If yes,

2x^2+3x-4=16
2x^2+3x = 20
-5(2x^2+3x)= -100
-10x^2-15x = -100

9 (c) 的答案不對,
(p+q)(12p+12q-16)
=4(p+q)(3p+3q-4)
因為因式分解需將公因式抽出。