x^4+√5x^3-11x^2-√5x+10
=x^4-11x^2+10+√5x^3-√5x
=(x^2-10)(x^2-1)+√5x(x^2-1)
=(x^2-10+√5x)(x^2-1)
=(x+1)(x-1)(x^2+√5x-10)