有4條數唔識

1.3+x^3+x^2+3x
=x^2(1+x)+3(1+x)
=(1+x)(x^2+3)

2.2bc-2ac+3a-3b (你應該抄錯題~)
=2c(b-a)-3(b-a)
=(b-a)(2c-3)

3.4ax+6ay-6bx-9by
=2a(2x+3y)-3b(2x+3y)
=(2x+3y)(2a-3b)

4. 9x^2-3xy-6xy+2y^2
=3x(3x-y)-2y(3x-y)
=(3x-y)(3x-2y)

1) 3+x^3+x^2+3x
= x^3+x^2+3x +3
= x^2 (x+1) + 3 (x+1)
= (x^2+3)(x+1)
2) 2ac-2ac+3a-3b
= 0+3a-3b
= 3a-3b
= 3(a-b)
3) 4ax+6ay-6bx-9by
= 2a(2x+3y)-3b(2x+3y)
= (2a-3b)(2x+3y)
4) 9x^2-3xy-6xy+2y^2
This question has 2 method.

Method 1
9x^2-3xy-6xy+2y^2
= 3x(3x-y)-2y(3x-y)
= (3x-y)(3x-2y)

Method 2
9x^2-3xy-6xy+2y^2
= 9x^2-9xy+2y^2
Use acx^2 +(bc+ad)x +bd = (ax+b)(cx+d)
9x^2-9xy+2y^2
= (3x-y)(3x-2y)
3 -1
3 -2
(交叉相乘)

1) x^3 + x^2 + 3x + 3
= x^2 (x + 1) + 3 (x + 1)
= (x^2 + 3) (x + 1)

（２尼條有無寫錯？）
2) 2ac - 2ac + 3a - 3b
= 0 + 3a - 3b
= 3 (a - b)

（定係應該咁？）
2) 2ac - 2bc + 3a - 3b
= 2c (a - b) + 3 (a - b)
= (2c + 3) (a - b)

4) 4ax + 6ay - 6bx - 9by
= (4ax + 6ay) - (6bx + 9by)
= 2a (2x + 3y) - 3b (2x + 3y)
= (2a - 3b) (2x + 3y)

5) 9x^2 - 3xy - 6xy + 2y^2
= (9x^2 - 3xy) - (6xy - 2y^2)
= 3x (3x - y) - 2y (3x - y)
= (3x - 2y) (3x - y)

enjoy =)