solve 3 nonlinear equation symbolic

Question

mojan marghoub shadkar 2021-7-26

0
链接

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https://ww2.mathworks.cn/matlabcentral/answers/886034-solve-3-nonlinear-equation-symbolic

回答： Shravan Kumar Vankaramoni 2021-8-2

Hi,

I want to find the variable Fw,Fi,Fr for following equations. I do not have the value for the other parameters , so I want to solve it as a symbolic equation, but when I use the solve funciton matlab gave me a this error " Unable to find explicit solution".

The goal is find fi fw fr symbolic.

My equations are

%

syms vr vw vi dw di dr d m n w v r rw vp1 vp2 va a

syms fi fw fr

eq1=-v+(-(((vr^2)*(vw^2)*(vi^2)*dw*di*dr)/(d*((vr^2)*(dr)*((1-fr))*((fw/(1-fr))-1)*(dw)*(vw^2))-((fw/(1-fr))*di*(vi^2)))+(di*dw*(vw^2)*(vi^2)*(1-fr))-(di*dw*(vw^2)*(vi^2)))*(vr*vw*vi)/((-(fw/(1-fr))*vw)+((fw/(1-fr))*vi)+(vw))*(vr*(1-fr))+(vw*vi*(-(1-fr)))+(vw*vi))/(((1-fr)*(vr*vw*vi)/((-(fw/(1-fr))*vw)+((fw/(1-fr))*vi)+(vw))*(vr*(1-fr))+(vw*vi*(-(1-fr)))+(vw*vi)*w*((fw/(1-fr))^n))-((1-fr)*-(((vr^2)*(vw^2)*(vi^2)*dw*di*dr)/(d*((vr^2)*(dr)*((1-fr))*((fw/(1-fr))-1)*(dw)*(vw^2))-((fw/(1-fr))*di*(vi^2)))+(di*dw*(vw^2)*(vi^2)*(1-fr))-(di*dw*(vw^2)*(vi^2)))*w*((fw/(1-fr))^n))+-(((vr^2)*(vw^2)*(vi^2)*dw*di*dr)/(d*((vr^2)*(dr)*((1-fr))*((fw/(1-fr))-1)*(dw)*(vw^2))-((fw/(1-fr))*di*(vi^2)))+(di*dw*(vw^2)*(vi^2)*(1-fr))-(di*dw*(vw^2)*(vi^2))));

eq2=(rw)*((1-fr)^(-m))*((fw/1-fr)^(-n))-r;

eq3=fr+fw+fi-1;

s= solve(eq1,eq2,eq3,fw,fi,fr,'ReturnConditions', true)

Thanks