1、(x+y)^2+6(x+y)+9
=〔(x+y)+3〕^2
=(x+y+3)^2
2、 a^2-2a(b+c)+(b+c)^2
= 〔a-(b+c)〕^2
= (a-b-c)^2
3、 4xy^2-4x^2*y-y^3
= -y(-4xy+4x^2+...
1、(x+y)^2+6(x+y)+9
=〔(x+y)+3〕^2
=(x+y+3)^2
2、 a^2-2a(b+c)+(b+c)^2
= 〔a-(b+c)〕^2
= (a-b-c)^2
3、 4xy^2-4x^2*y-y^3
= -y(-4xy+4x^2+...