[20] Factorization

1. 6a^2 + 6 - 4a - 9a
=2a(3a-2)+3(2-3a)
=2a(3a-2)-3(3a-2)
=(2a-3)(3a-2)

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

3. 2x^3 + x^2 + 8x + 4
=x^2(2x+1)+4(2x+1)
=(x^2+4)(2x+1)

4. cd^2 - c^2 d - c +d
=d(cd+1)-c(cd+1)
=(d-c)(cd+1)

5. 36h^2 k + 12k - 3hk^2 - 144h
=36h(hk-4)+3k(hk-4)
=36h(hk-4)-3k(hk-4)
=(36h-3k)(hk-4)

6. -30ax^2 + 3a^2 bc + 6abcx - 15a^2 x
=-15ax(2x+a)+3abc(a+2x)
=-(15ax-3abc)(2x+a)

7. cy^2 - dy^2 + cy - c +d - dy
=cy^2+cy-c-dy^2+d-dy
=c(y^2+y-1)-d(y^2-1+y)
=(c-d)(y^2+y-1)

8. x^2 + ax - bx + xy - by - ab
=x^2+xy+ax-bx-ab-by
=x(x+y+a)-b(x+a+y)
=(x-b)(x+y+a)

1. 6a^2 + 6 - 4a - 9a
= 6a^2-4a+6-9a
= 2a(3a-2)+3(2-3a)
= 2a(3a-2)-3(3a-2)
= (2a-3)(3a-2)

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

3. 2x^3 + x^2 + 8x + 4
= x^2(2x+1)+4(2x+1)
= (x^2+4)(2x+1)

4. cd^2 - c^2 d - c +d
= cd^2+d-c^2d-c
= d(cd+1)-c(cd+1)
= (d-c)(cd+1)

5. 36h^2 k + 12k - 3hk^2 - 144h
= 36h^2k-144h+12k-3hk^2
= 36h(hk-4)+3k(4-hk)
= 36h(hk-4)-3k(hk-4)
= (36h-3k)(hk-4)

6. -30ax^2 + 3a^2 bc + 6abcx - 15a^2 x
= 3a^2bc-15a^2x-30ax^2+6abcx
= 3a^2(bc-5x)-6ax(5x-bc)
= 3a^2(bc-5x)+6ax(bc-5x)
= (3a^2+6ax)(bc-5x)

7. cy^2 - dy^2 + cy - c +d - dy
= y^2(c-d)+cy-dy-(c-d)
= y^2(c-d)+y(c-d)-(c-d)
= (y^2+y-1)(c-d)

8. x^2 + ax - bx + xy - by - ab
= x^2-bx+ax-ab+xy-by
= x(x-b)+a(x-b)+y(x-b)
= (x+a+y)(x-b)

Tips 1 排番好佢再抽出黎
Tips 2 注意 + - 個d附號