1.原式=[2（x+y）+（x-y）][ 2（x+y）-（x-y）]
=(3x-y)(x+3y)
2.原式=9a^2b^4-6ab^2+1
=(3ab^2-1)^2
3.原式=[(m/3)^2+n]^2
4.原式=（4x^2-9y^2）-(2x+3y)
=(2x+3y)(2x-3y) -(2x+3y)
=((2x+3y)(2x-3y-1)
5.原式=(x+√a)(x-√a)
6.原式=x^2-y^2+2x+1
=( x^2+2x+1)- y^2
=(x+1)^2- y^2
=( x+y+1)( x-y+1)
7.原式=(x+y+z+x-y+z)( x+y+z-x+y-z)
=(2x+2z)2y
=4(x+z)y
8.原式=5x^3-5=5(x^3-1)
= 5(x-1)(x^2+x+1)
9.原式=( x^3-y^3)-(x^2+xy+y^2)
= (x-y)(x^2+xy+y^2) -(x^2+xy+y^2)
=(x^2+xy+y^2)(x-y-1)
10.2(x^3+y^3)
=2 (x+y)(x^2-xy+y^2)
11.原式=(x^3-1)-2x（x-1）
=(x-1)(x^2+x+1)-2x(x-1)
=(x-1) (x^2+x+1-2x)
=(x-1) (x^2-x+1)