原式=x^4(x+1)+x^2(x+1)+(x+1)
=(x+1)(x^4+x^2+1)
=(x+1)(x^4+2x^2+1-x^2)
=(x+1)[(x^2+1)^2-x^2]
=(x+1)(x^2+x+1)(x^1-x+1)