用Forcal求解很简单：
!using["fcopt"];
c: cf(z,y)= y=z^3+(-3+3i)*z^2+(-1-8i)*z+(-1+7i);
cc(x,y,y1,y2)= cf(x,y,&y1,&y2);
solve[HFor("cc"), optmode,5, optdeep,5];

结果（实部，虚部，误差）：
-0.6435942529055819       -2.553773974030037        0.
0.6435942529055827        0.5537739740300375        0.
3.                        -1.                       2.51214793389404e-015