x^5+x+1
＝x^5-x^2+x^2+x+1
=x^2(x^3-1)+(x^2+x+1)
=x^2*(x-1)(x^2+x+1)+(x^2+x+1)
=(x^2+x+1)(x^3-x^2+1)
x^3+5x^2+3x-9
=(x^3-1)+(5x^2+3x-8)
=(x-1)(x^2+x+1)+(5x+8)(x-1)
=(x-1)(x^2+x+1+5x+8)
=(x-1)(x^2+6x+9)
=(x-1)(x+3)^2