求助数学解答题.关于因式分解
(a+b)2(a-b)+(a-b)2(a+b)
(x+y)2-4y2
(m+2n)2+2(m+2n)(2m+n)+(2m+n)2
x2+2xy+y2-4x-4y-5
a4-a2-72
x2-3x3-9+27x