Solve a system of two variable inequalities with symbolic toolbox

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

Answer 1

[John D'Errico]

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),'.')

[LUCA D'AMBROSIO]

hi, sorry to bother you, thank you for your answer.

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.

thank you for your help

Answer 2

[Torsten]

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.