F.2 maths.....!!!!趕!!!

(x - 3)^2 - 4x^2

= (x - 3)^2 - (2x)^2

= (x - 3 - 2x)(x - 3 + 2x)

= (-x - 3)(3x - 3)

= -(x + 3)3(x - 1)

= -3(x + 3)(x - 1)

2007-03-08 19:02:16 補充：
THe above answer is wrong because 4x^2 does not equals to (4x)^2 but 4*x^2

我不明白閣下究竟想問什麼
要factorisation還是直接拆括號
我兩者皆做:
因式分解:
(x-3)²-4x²
=(x-3)²-(2x)²
=(x-3+2x)(x-3-2x) (Because (a+b)(a-b)=a²-b²)
=-(3x-3)(x+3)
拆括號:
(x-3)²-4x²
=(x²-6x+9)-4x²
=x²-6x+9-4x²
=-3x²-6x+9

2007-03-08 19:12:58 補充：
不好意思,差了一點:-(3x-3)(x十3)=-3(x-1)(x十3)二樓:閣下錯了,x-3絕不等於x²-9

(X-3)^2-4X^2
= X^2-9-4X^2
= -3X^2-9

仲有,我只係F.1=.=