1、x(x+4)+4=x ²+4x+4=(x+2)²2、2mx²-4mxy+2my² =2m(x²+2xy+y²)=2m(x+y)²3、x三次方y+2x平方y平方+xy三次方=xy(x²+2xy+y²)=xy(x+y)²