Because x 1, x2 satisfies the meta-equation, x12 =-3x1-1,which brings the required formula:

x 1^3+8×x2+20

=(-3×x 1— 1)×x 1+8×x2+20

=—3(x 1^2+3×x 1+ 1)+8(x 1+x2)+23

Because x12+3× x1+1= 0, x1+x2 =-3;

therefore

Original formula =- 1.