因式分解!!!快d答牙!!!!好趕牙!!!

1.a²b²-2ab²+b²
=(ab)²-2(ab)(b)+b²
=(ab-b)²
=b²(a-1)²
2. (x-3y)³-(x+3y)³
=[(x-3y)-(x+3y)][(x-3y)²+(x-3y)(x+3y)+(x+3y)²]
=(-6y)(x²-6xy+9y²+x²-(3y)²+x²+6xy+9y²)
=(-6y)(3x²+27y²)
=(-18y)(x²+9y²)
3. 6-x-x²
=(2-x)(3+x) (by cross method)
4. 6- (a-2) -(a-2)²
=6-[(a-2)+(a-2)²]
=6-(a-2)(a-1)
=6-(a²-3y+2)
=-a²+3y+4
=(4-a)(1+a)

1.
a²b²-2ab²+b²
= (ab)²-2(ab)(b)+b²
= (ab-b)²
= b²(a-1)²

2.
(x-3y)³-(x+3y)³
= [(x-3y)-(x+3y)][(x-3y)² + (x-3y)(x+3y) + (x+3y)²]
= (x-3y-x-3y)[(x²-6xy+9y²) + x² - (3y)² + (x²+6xy+9y²)]
= (-6y) (x²-6xy+9y²+x²-9y²+x²+6xy+9y²)
= (-6y)(3x²+9y²)
= (3)(-6y)(x²+3y²)
= (-18y)(x²+3y²)

3.
方法一: (用十字相乘法)
6-x-x²
= (2-x)(3+x)
方法二:
6-x-x²
= 6+2x-3x-x²
= 2(3+x)-x(3+x)
= (3+x)(2-x)

4.
6 - (a-2) - (a-2)²
方法一: (用十字相乘法)
6 - (a-2) - (a-2)²
= [2 - (a-2)][3 + (a-2)]
= (2 - a + 2)(3 + a - 2)
= (4 - a)(a +1)

方法二:
可用第3題的答案, 以a-2代入 x中:
= [3+(a-2)][2-(a-2)]
= (3+a-2)(2-a+2)
= (a+1)(-a+4)
= (a+1)(4-a)

有錯請指正!