Question 20If $y=x+\dfrac1x,$ then $x^4+x^3-4x^2+x+1=0$ becomes:$x^2(y^2+y-2)=0$$x^2(y^2+y-3)=0$$x^2(y^2+y-4)=0$$x^2(y^2+y-6)=0$none of these