a^4-4a^3+a^2+4a=?
问题描述:
a^4-4a^3+a^2+4a=?
答
a^4-4a^3+a^2+4a=a^4+a^2-4a(a^2+1)
=a^2(a^2+1)-4a(a^2+1)
=(a^2+1)(a^2-4a)
=a(a^2+1)(a-4)