Solving Inequalities using symbolic tool box

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Jagadeesh Korukonda
Jagadeesh Korukonda 2023-10-28
评论： Walter Roberson 2023-10-31
Ran in:
When I try to solve simple inequality
let say
the solution is
but matlab is giving wierd answers
syms x
solve(x^2 - 25>0,x)
ans = 
can somone help me, how to fix this issue?
  2 个评论
Torsten
Torsten 2023-10-28
Ran in:
syms x real
sol = solve(x^2 - 25>0,x,'ReturnConditions',1);
sol = struct with fields:
x: [2×1 sym] parameters: x conditions: [2×1 sym]
sol.x(1)
ans = 
x
sol.x(2)
ans = 
x
sol.conditions
ans = 

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回答（1 个）

Walter Roberson
Walter Roberson 2023-10-31
It is common with the symbolic engine that in practice you need to convert inequalities into equalities by introducing a non-negative or a positive "excess" variable -- so if f(x) > y(x) then f(x) - y(x) > 0; let δ quantify how much more so f(x) - y(x) = delta for positive delta. Now you can try to solve() your system for the other variables and you will get back a system of solutions in terms of the quantified-excess variables
  1 个评论
Walter Roberson
Walter Roberson 2023-10-31
Ran in:
syms x real
syms delta positive
eqn = x^2 - 25 == delta %amount difference of terms is greater than 0
eqn = 
sol = solve(eqn, x)
sol = 

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