function F=AA(x)
x1=x(1);
x2=x(2);
x3=x(3);
x4=x(4);
x5=x(5);
F1=[x1/(5+x1-x3-x4-x5)-0.0187
(x2+2*x3-2*x4)/(5-x2-3*x3-x4)-1.35*10^7
(x2+2*x3-2*x4)^2*(5+x1-x3-x4-x5)/(5-x2-3*x3-x4)^3-9.43*10^18
(2*x4-x5)^2*(5+x1-x3-x4-x5)/((x2+2*x3-2*x4)^2*(5-x2-3*x3-x4))-5.38*10^(-4)
(5+x1-x3-x4-x5)/(2*x4-x5)-37.5];
%=====================
x0=[2.1 100 2 0.8 2.1];%你的方程初值很重要；
opt=optimset('Algorithm','Levenberg-Marquardt','MaxIter',1e4, 'TolFun',1e-6);
[X,FVAL,EXITFLAG] = fsolve(@AA,x0,opt)