2楼: Originally posted by hppdyx at 2013-12-19 09:21:58
我试过，应该是你的torlerance太小了，默认是1e-4，但是你的参数都太小。所以可以把torlerance减小。我试过,结果是x= 4.5759和0.4939，不知道对不对。

options = optimset('TolFun', 1e-10);
x=fsolve(@concen ...

Constant a1=5.28E-05, a2=-6.22E-06, a3=-1.05E-05, b1=2.96E-05, b2=-3.79E-06,
         b3=-3.79E-06, b4=-1.05E-05, b5=-8.81E-06;
Function a1+a2*x1+a3*x1*x2;
         b1+b2*x2+b3*x2^(3/2)+b4*x1*x2+b5*x2^2;

4楼: Originally posted by dingd at 2013-12-19 09:45:09
试试1stOpt，不需初值，简单易用：

Constant a1=5.28E-05, a2=-6.22E-06, a3=-1.05E-05, b1=2.96E-05, b2=-3.79E-06,
         b3=-3.79E-06, b4=-1.05E-05, b5=-8.81E-06;
Function a1+a2*x1+a3*x1*x2;
     ...