(1)(m+n)^-4m(m+n)+4m^
问题描述：
(1)(m+n)^-4m(m+n)+4m^
(2)a^+2a(b+c)+(b+c)^
(3)4+12(x-y)+9(x-y)^
(4)(a-b)(x-y)-(b-a)(x+y)
答
1.[（m+n)-2m]
2.[a+(b+c)]
3.[2+（x-y)]
4.(a-b)(x-y+x+y)
=2x(a-b)