# Solve a system of two variable inequalities with symbolic toolbox

4 ビュー (過去 30 日間)
LUCA D'AMBROSIO 2024 年 7 月 1 日
コメント済み: LUCA D'AMBROSIO 2024 年 7 月 2 日
Hello,
is it possible to symbolically solve a system of inequalities with variables x and y and plot the result?
lets say i have to solve x+y-25>0 and x*y+y+15>0, what function should i use?
i have tried fimplicit plus assumptions but it didn't work.
thank you

サインインしてコメントする。

### 採用された回答

John D'Errico 2024 年 7 月 1 日
fimplicit does not plot inequalities. Sorry. If you read the help, it never says anything about inequalities.
Simplest is to just use meshgrid. For example...
[X,Y] = meshgrid(linspace(-50,50,1000));
k = (X + Y - 25 > 0) & (X.*Y + Y + 15 > 0);
plot(X(k),Y(k),'.')
##### 1 件のコメント-1 件の古いコメントを表示-1 件の古いコメントを非表示
LUCA D'AMBROSIO 2024 年 7 月 2 日
do you know if there is a way to extract only the boundary of the region highlighted in the figure? i figured i don't need all the points where both inequalities are satisfied but only the curve where they are equal to zero, so the boundary and i need to check how this boundary evolves with some variyng constants.

サインインしてコメントする。

### その他の回答 (1 件)

Torsten 2024 年 7 月 1 日

is it possible to symbolically solve a system of inequalities with variables x and y ?
What do you mean by "solve" ? The feasible set is given by the set of inequalities, and in most cases it is not possible to find an easier representation.

サインインしてコメントする。

### カテゴリ

Help Center および File ExchangeSymbolic Math Toolbox についてさらに検索

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by