因式分解x^4-6x^3+x^2+7
问题描述：
因式分解x^4-6x^3+x^2+7
答
x^4-6x^3十x^2十7
=x^4-2x^3十x^2-4x^3十4十3
=x^2(x-1)^2-4(x-1)(x^2十x十1)十3
=(x-1)(x^3-5x^2-4x-4)十3