Solving Inequalities with Matlab

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

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.

https://fr.mathworks.com/matlabcentral/answers/94721-is-there-a-method-for-solving-inequalities-using-the-symbolic-math-toolbox-5-6-r2011a

Is there a way to use a Matlab function, not necessarily solve to get the correct domain? Thank you very much.

Answer 1

[Dyuman Joshi]

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)

sol = struct with fields:
             x: x
    parameters: x
    conditions: x < 0 & -4 < x

[Dimitrios Anagnostou]

Thanks a lot. Is it anywhere documented this setting?

[Dyuman Joshi]

Yes, refer to Solving Inequalities - documentation solve

[Steven Lord]

Yes, on the documentation page for the solve function. This documentation page also includes an example, "Solve Inequalities", that shows its use.

[Walter Roberson]

https://www.mathworks.com/help/symbolic/sym.solve.html#buezrr6-ReturnConditions