What solver to use for parabolic equation?

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Fafar 2013-11-20

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https://ww2.mathworks.cn/matlabcentral/answers/106876-what-solver-to-use-for-parabolic-equation

回答： Deepak Ramaswamy 2013-11-22

采纳的回答： Walter Roberson

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Greetings, I have the following equation that I need to solve

1000/((x/10)^(20/19) + ((9*x)/10)^(100/97)) - x = 0

I tried using the following but it took forever and didn't return an answer:

syms x
solve(1000/((x/10)^(20/19) + ((9*x)/10)^(100/97)) - x)

if you plot the equation there is an answer around 30

ezplot(1000/((x/10)^(20/19) + ((9*x)/10)^(100/97)) - x,10,100)

but I cannot seem to find it using the solver.

Thanks in advance

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Answer 1

Walter Roberson 2013-11-20

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I am pretty sure there is no closed form solution to that. You will probably need to use a numeric solver.

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Fafar 2013-11-20

thanks. can you elaborate on how to do that?

Walter Roberson 2013-11-20

See fzero() or fsolve(). Or if you want to work symbolically, the MuPAD command numeric::solver (note: there is no MATLAB interface for that.)

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Answer 2

Deepak Ramaswamy 2013-11-22

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You can try vpasolve, Symbolic Math Toolbox's numeric solver. This returns - 30.078324091827534639885832779983 + 1.5357472679395261619060458042632*I. If you subs the solution back in to the equation, you get - 1.7632415262334312619531048058334e-38 + 5.8774717541114375398436826861112e-39*I which is close to zero