The bi quadratic equation, two of whose roots are 1+i, 1−2  is

1±i,1±2 are the roots of the given equation   hence the required equation is =x-1+ix-1-ix-1+2x-1-2=0⇒x2-2x+2x2-2x-1=0⇒x4−4x3+5x2−2x−2=0