1.x(x-y)(y-x+y)=x(x-y)(2y-x)
2.(x-6y)^2
3.a^2+8ab=a(a+8b)
4.(a^2+b^2+2ab)(a^2+b^2-2ab)=(a+b)^2(a-b)^2=(a^2-b^2)^2
5.2[(a-1)^2-6(a-1)+9]=2[(a-1)-3]^2=2(a-4)^2
6.3(x^2+4xy+4y^2)=3(x+2y)^2