Why the responses of the following equations are nothing?

Question

Marzieh Nodeh 2022-4-21

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1702015-why-the-responses-of-the-following-equations-are-nothing

评论： Star Strider 2022-4-25

I'm trying to find aeq from the following equations. There are 3 equations with 3 unknowns. but the final response is empty brackets for all unknowns. Could you help me to solve this equation.

Regards,

syms ae gama A
eq1= (23.4255*(ae^3))+(1.2308e-06*ae)+gama
eq2= (A/(6*23.4255))-((2*1.2308e-06)/A)-ae
eq3= A-((((-108*gama)+(12*(sqrt(3*(((4*(1.2308e-06^2))+(27*(gama^2)*23.4255))/23.4255)))))*(23.4255^2)))^(1/3)
eqs= [eq1, eq2, eq3]
[ae,gama,A]=vpasolve(eqs, [ae,gama,A])
%reported results
ae =
 
[ empty sym ]
 
gama =
     []
A =
     []

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Answer 1

Star Strider 2022-4-21

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1702015-why-the-responses-of-the-following-equations-are-nothing#answer_947910

在 MATLAB Online 中打开

Use solve then vpa —

syms ae gama A

eq1= (23.4255*(ae^3))+(1.2308e-06*ae)+gama

eq1 =

eq2= (A/(6*23.4255))-((2*1.2308e-06)/A)-ae

eq2 =

eq3= A-((((-108*gama)+(12*(sqrt(3*(((4*(1.2308e-06^2))+(27*(gama^2)*23.4255))/23.4255)))))*(23.4255^2)))^(1/3)

eq3 =

eqs= [eq1, eq2, eq3]

eqs =

[ae,gama,A]=solve(eqs, [ae,gama,A]);

Warning: Possibly spurious solutions.

ae = vpa(ae,7)

ae =

gama = vpa(gama,7)

gama =

A = vpa(A,7)

A =

Also consider double instead of vpa, depending on the result you want.

.

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Marzieh Nodeh 2022-4-25

在 MATLAB Online 中打开

I didn't change the problem.

syms ae gama A
eq1= (23.4255*(ae^3))+(1.2308e-06*ae)+gama
eq2= (A/(6*23.4255))-((2*1.2308e-06)/A)-ae
eq3= A-((((-108*gama)+(12*(sqrt(3*(((4*(1.2308e-06^2))+(27*(gama^2)*23.4255))/23.4255)))))*(23.4255^2)))^(1/3)
eqs= [eq1, eq2, eq3]
 
eq1 =
 
(46851*ae^3)/2000 + (5812288667115959*ae)/4722366482869645213696 + gama
 
 
eq2 =
 
(8796093022208*A)/1236317262550401 - ae - 5812288667115959/(2361183241434822606848*A)
 
 
eq3 =
 
A - ((14480675016937209*(81*gama^2 + 468829135928447625/604153424797493242284363218944)^(1/2))/2199023255552 - (130326075152434881*gama)/2199023255552)^(1/3)
 
 
eqs =
 
[ (46851*ae^3)/2000 + (5812288667115959*ae)/4722366482869645213696 + gama, (8796093022208*A)/1236317262550401 - ae - 5812288667115959/(2361183241434822606848*A), A - ((14480675016937209*(81*gama^2 + 468829135928447625/604153424797493242284363218944)^(1/2))/2199023255552 - (130326075152434881*gama)/2199023255552)^(1/3)]
 
>> [ae,gama,A]=solve(eqs, [ae,gama,A]);
Warning: 6 equations in 3 variables. 
> In C:\Program Files\MATLAB\R2013a\toolbox\symbolic\symbolic\symengine.p>symengine at 56
  In mupadengine.mupadengine>mupadengine.evalin at 97
  In mupadengine.mupadengine>mupadengine.feval at 150
  In solve at 170 
Warning: Explicit solution could not be found. 
> In solve at 179 