# how to solve an equation by using trial and error method?

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Ali Deniz on 16 May 2022
Commented: Ali Deniz on 16 May 2022
𝑇ℎ𝑟𝑜𝑎𝑡 (𝐴∗)=647.5 𝑚𝑚2
A=1027.5 mm^2
How can I calculate 𝑀𝑥 value by using trial and error method or how can I find the value of Mx by another method. Thank you.
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### Accepted Answer

Sam Chak on 16 May 2022
I'm not sure what the trial-and-error method is for this, but I think that basic Algebraic methods can be used to rearrange the equation. I followed the example in fzero and make an assumption:
% Assume
gamma = 1.55526564459735;
% function to be solved
f = @(M) (1/M)*((2*(1 + (gamma - 1)/2*M^2))/(gamma + 1))^((gamma + 1)/(2*(gamma - 1))) - Ax/Astar;
% initial guess
M0 = 3;
% root-finding solver
Msol = fzero(f, M0)
There should be two real roots.
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Ali Deniz on 16 May 2022
Thank you.
-Ali

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### More Answers (1)

Walter Roberson on 16 May 2022
Multiply both sides by Mx. Subtract the left side from the right. Expand out. You now have a polynomial of degree 2 in Mx.
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Walter Roberson on 16 May 2022
Ah, I am on mobile. I had tried scrolling the image but it didn't scroll so I didn't see the power.

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