x^4+x^3+x^2-1=x^4-1+x^3+x^2=(x^2+1)(x^2-1)+x^2(x+1)=(x^2+1)(x^2-1)+x^2(x+1)=(x^2+1)(x+1)(x-1)+x^2(x+1)=(x+1)(x^3-x^2+x-1+x^2)=(x+1)(x^3+x-1)
(x的立方+x-1)(x+1)
=x的3次方(x+1)+(x+1)(x-1)=(x+1)(x的3次方+x-1)
x^3(x^+1)+(x+1)(x—1)=(x^3+x+1)(x-1)