分解因式8a-4a^-49(x+y)^-81(x-y)^4b^c^-(b^+c^-a^)^求证：任意两个奇数的平方差是8

1.8a-4a^-4= -4（a^-2a+1）=-4（a-1）^
2.9(x+y)^-81(x-y)^ =[3(x+y)]^-[9(x-y)]^
=(3x+3y+9x-9y)(3x+3y-9x+9y)=(12x-6y)(12y-6x)=36(2x-y)(2y-x)
3.4b^c^-(b^+c^-a^)^ =(2bc)^-(b^+c^-a^)^
=(2bc+b^+c^-a^)(2bc-b^-c^+a^)=[(b+c)^-a^][a^-(b-x)^]
=(b+c+a)(b+c-a)(a+b-c)(a-b+c)
4.(2n+1)^-(2n-1)^=4n*2=8n所以是8的倍数

8a-4a^-4=-4（a^-2a+1）=-4（a-1）^

8a-4a^2-4=-4（a^2-2a+1）=-4（a-1）^2
[3(x+y)+9(x-y)]*[3(x+y)-9(x-y)]=(12x-6y)(12y-6x)
(2bc+b^2+c^2-a^2)(2bc-b^2-c^2+a^2)