х^4=x^3+2x^2+x^3+x^2=2x+x^2+x+2=12

x^4+2x^3+4x^2+3x+2=12

x^4+2x^3+4x^2+3x+2-12=0

x^3*(x-1)+3x^2*(x-1)+7x*(x-1)+10(x-1)=0

(x-1)(x^3+2x^2+x^2+2x+5x+10)=0

(x-1)*(x+2)(x^2+x+5)=0

x-1+0

x+2+0

x^2+x+5=0

x+1

x+-2

x нету корней

x=-2

x=1

one x=-2

two x=1