a^8-1
(a^4+1)(a^4-1)
=(a^4+1)(a^2+1)(a^2-1)
=(a^4+1)(a^2+1)(a+1)(a-1)还有一题：y^2(m-2)+(2-m)..因式分解y^2(m-2)+(2-m)..=y^2(m-2)-(m-2)=(m-2)(y^2-1)=(m-2)(y+1)(y-1)