1) 2(x+y)^2
2)16-x^4/81=(4-x^2/9)(4+x^2/9)
3)(x-2y)(x^2+2xy+4y^2)
4) 2(x+y)+x^2-y^2=2(x+y)+(x-y)(x+y)=(x+y)(x-y+2)
1) 2(x+y)^2
2)16-x^4/81=(4-x^2/9)(4+x^2/9)
3)(x-2y)(x^2+2xy+4y^2)
4) 2(x+y)+x^2-y^2=2(x+y)+(x-y)(x+y)=(x+y)(x-y+2)