how to solve a linear system with a maximum function

2018 3 9
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更新时间：2018 3 9
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just i want to know how we solve this system:
x+y = 1
max(x,y)=2
i tried this code but an error always appear:
syms x y
solve(x+y ==1,max(x,y)==2)
//Error using sym/max (line 97)
Input arguments must be convertible to floating-point numbers
any help ?

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Rik
Rik 2018-3-9
max(x,y) can be rewritten to (x>y)*x+(x<=y)*y
syms x y
solve([x+y ==1,(x>y)*x+(x<=y)*y ==2])
But alas, this doesn't work either:
Error using mupadengine/feval (line 187)
System contains an equation of an unknown type.
Fatima Hammoud
Fatima Hammoud 2018-3-9
thanks for your try, i appreciate that
Rik
Rik 2018-3-9
Substituting the solutions, it indeed solves it, so you can add it as the answer, Torsten.
Fatima Hammoud
Fatima Hammoud 2018-3-9
Rik , can you explain to me more ? did you find the solution ?

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 采纳的回答

Torsten
Torsten 2018-3-9
编辑：Torsten 2018-3-9

0 个投票

syms x y
[solx, soly] = solve([x+y==1,piecewise(x>y,x,y)==2],[x y])
Best wishes
Torsten.

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Fatima Hammoud
Fatima Hammoud 2018-3-9
Thank you sir for your help, but 'piecewise' is Undefined function or variable in Matlab , are you using MuPAD?
Torsten
Torsten 2018-3-9
Maybe you use an older MATLAB version ?
https://de.mathworks.com/help/symbolic/piecewise.html
Best wishes
Torsten.
Fatima Hammoud
Fatima Hammoud 2018-3-9
That's weird i'm using R2016a !!
Any way, thank you.

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