初二分解因式求解。急需！！！！

1. y^2 - 9(x+y)^2=[y+3(x+y)][y-3(x+y)]=-(3x+4y)( 3x+2y)
2.（x+y+z)^2 -(x-y-z)^2 =[(x+y+z)+(x-y-z)][(x+y+z)-(x-y-z)]=4x(y+z)
3.(x+y)^2 -14(x+y) +49=(x+y-7)^2
4.(a^2 +4)^2 - 16a^2 =(a^2+4a+4)(a^2-4a+4)=(a+2)^2(a-2)^2
5. 9+6(a+b)+(a+b)^2=(a+b+3)^2

1
(y+3x+3y)*(y-3x-3y)
2
(x+y+z+x-y-z)*(x+y+z-x+y+z)
3
(x+y-7)(x+y-7)
4
((a^2 +4+4a)*((a^2 +4-4a)
=(a+2a)^2*(a-2a)^2
5
(a+b+3)(a+b+3)

1,=-(9X^2=+18xy+8y^2)
=-(3x+2y)(3x+4y)
2,=x^2+y^2+z^2+2xy+2yz+2xZ-X^2-y^2-Z^2+2xy+2xz-2yz
=4xy+4xz
=4x(Y+z)
3,=(x+y-7)^2
4.=(a^2 +4)^2 - 16a^2
=(a^2+4-4a)(a^2+4+4a)
=(a-2)^2(a+2)^2
5,=(3+a+b)^2 有些一步就出来了，没过程