Solving Inequalities with Matlab
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Dimitrios Anagnostou
on 27 Mar 2023
Commented: Walter Roberson
on 27 Mar 2023
I guess this is a frequent question here but the answers I have seen did not help me.
I want to solve the following inequality: |x-2| > 2|x+1|.
Manually, we get
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/1337729/image.png)
In Mathematica there is the built-in function Reduce.
In[58]:= Reduce[Abs[x - 2] > 2 Abs[x + 1], x, Reals]
Out[58]= -4 < x < 0
With Matlab I get
>> version
ans =
'9.13.0.2105380 (R2022b) Update 2'
>> syms x real
>> solve(abs(x-2) > 2*abs(x+1), x)
ans =
-2
There is this answer here that uses Mupad's Solve function but apparently it does not work anymore.
Is there a way to use a Matlab function, not necessarily solve to get the correct domain? Thank you very much.
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Accepted Answer
Dyuman Joshi
on 27 Mar 2023
You need to use 'ReturnConditions' as true to obtain the conditions on the solution
syms x real
sol=solve(abs(x-2) > 2*abs(x+1), x,'ReturnConditions',true)
4 Comments
Steven Lord
on 27 Mar 2023
Yes, on the documentation page for the solve function. This documentation page also includes an example, "Solve Inequalities", that shows its use.
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