C1=7.0863;
C2=6.8971;
C3=0.4929;
C4=0.8131;
C5=1.8240;
C6=3.8108;
C7=3.7318;
C8=-2.2238;
C9=1.9905;
C10=1.9087;
C11=0.6778;
syms X1 X2 X3;
//symbols x=sym("x")
exp1 = C1X1+C4X2-C5X3^2-C6X3-C9;
exp2 = C2X1+C4X2-C5X3^2-C7X3-C10;
exp3 = C3X1+C4X2-C5X3^2-C8X3-C11;
[X1,X2,X3] = solve(exp1,exp2,exp3,'X1,X2,X3'); % 直接用 solve 解决
x1 = double(X1)
x2 = double(X2)
x3 = double(X3)