factorize questions! 請教教在下

1. (x^2-x)^2 - 4(x^2-x)-12
= [(x^2-x) - 6][(x^2-x) + 2]
= [x^2 - x - 6][x^2 - x + 2]
= (x-3)(x+2)(x^2 -x + 2)

2. 3x^4y - 243y
= 3y(x^4 - 81)
=3y(x^2 + 9)(x^2 - 9)
=3y(x^2 + 9)(x + 3)(x - 3)

3. x^2y^2+14xyz- 15z^2
=(x^2y^2 - xyz) + (15xyz - 15z^2)
=xy(xy - z) + 15z(xy - z)
=(xy + 15z)(xy - z)

1.(x^2-x)^2 - 4(x^2-x)-12
=(x^2-x-6)(x^2-x+2)

抱歉....只幫到你第一題......

2006-12-13 22:20:02 補充：
第一題仲可以再factorize(x^2-x-6)(x^2-x+2)=(x-3)(x+2)(x^2-x+2)