11: =(x^2y^2)^2+2*x^2y^2*2+2
=(x^2y^2+2)^2
12: =(y-2)^2-x^2
=(y-2-x)(y-2+x)
13: =(1-3x)(1+3x+9x^2)
14: =(x-3+3)(x^2-6x+9-3x+9+9)
=x(x^2-3x+9)
15: =(3x+1)^3
16: =(1/3x^2-y)^3
17: =(2x-1+2)(4x^2-4x+1-4x+2+4)
=(2x+1)(4x^2-8x+7)
18: =(2x-1)^3
19: =(2x-1)^3-1
=(2x-1-1)(4x^2-4x+1+2x-1+1)
=(2x-2)(4x^2-2x+1)
=2(x-1)(4x^2-2x+1)