几道分解因式的题目，急求，加分。

（1）2y+3xy
= y(2+3x)

(2)2(a+2)+3b(a+2)
= (a+2)(2+3b)

(3)2a+4+3ab+6b
=2(a+2)+3b(a+20
=(a+2)(2+3b)

(4)x^2-9
= (x+3)(x-3)

(5)(a-2b)^2-9
=(a-2b+3)(a-2b-3)

(6)a^2-4ab+4b^2-9
= (a-2b)^2-3^2
=(a-2b+3)(a-2b-3)

(7)x^2-3x-4
=(x-4)(x+1)

(8)(a+b)^2-3(a+b)-4
=(a+b-4)(a+b+1)

(9)a^2+2ab+b^2-3a-3b-4
=(a+b)^2-3(a+b)-4
=(a+b-4)(a+b+1)

需过程，分解因式
(10)x^3+2x^2-2x-4
=x^2(x+2)-2(x+2)
=(x+2)(x^2-2)
=(x+2)(x+ √2)(X-√2)

(11)xy+2x+y+2
= x(y+2)+(y+2)
=(y+2)(x+1)

(12)6ab+4a+9b+6
= 2a(3b+2)+3(3b+2)
=(3b+2)(2a+3)

(13)6at+3bt-2as-bs
= 3t(2a+b)-s(2a+b)
=(2a+b)(3t-s)

(14)x^2-4y^2-x-2y
= (x+2y)(x-2y)-(x+2y)
=(x+2y)(x-2y-1)

(15)x^2-10xy+25y^2-3x+15y
=(x-5y)^2-3(x-5y)
=(x-5y)(x-5y-3)

都不是很难，看来有人想偷懒，呵呵