（x的4次方-1）/（x的3次方+x的平方+x+1）约分,
问题描述：
（x的4次方-1）/（x的3次方+x的平方+x+1）约分,
答
(x^4-1)/(x^3+x^2+x+1)
=(x^4-1)/[x^2(x+1)+(x+1)]
=(x^4-1)/[(x^2+1)(x+1)]
=(x^2+1)(x^2-1)/[(x^2+1)(x+1)]
=(x^2-1)/(x+1)
=(x+1)(x-1)/(x+1)
=x-1