how can I reach the unknown state by solving 2 inequalities in matlab?

Hi guys. I have two questions:

firstly : I wanna solve and inequal in matlab and I write below code:

clear all;
clc;
close all;
syms x1 x2 x3 x4
cond1=x1>36;
cond2=x2>8.5;
cond3=x3>0.05;
cond4=x4>2.2;
cond5=(x1*(-0.38*x1+0.04*x2-2.4*x3-0.028*x4))+(x2*(0.1*x1-0.01*x2+x3+0.011*x4)+(x3*(-0.06*x1+0.007*x2-0.742*x3-0.0065*x4)+x4*(-0.029*x1-0.028*x2-0.255*x3-0.086*x4)<=-10*(.5)*(x1.^2+x2.^2+x3.^2+x4.^2);
conds=[cond1 cond2 cond3 cond4 cond5];
sol=solve(conds,[x y],'ReturnConditions',true);
sol.x1
sol.x2
sol.x3
sol.x4
sol.x5
sol.parameters
sol.conditions

but it gives me this error:

Error: File: inequation.m Line: 14 Column: 193
Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

And my another questions is that assume that I want to solve 2 inequalities with a common unknown states besides other conds and I reach to the result of unknown state. For example in above problem, assum that this problem is the first problem in inequality in the right of it, instead of -10 I put an unknow state (K), and the second problem is like the first problem but I the limit for each of x1,x2,x3,x4 is as below

x1>30; x2>8;
x3>-9;
x4>4.5;
cond5=(x1*(-0.6988*x1+0.0518*x2-0.57*x3+0.0026*x4)+(x2*(0.32*x1-0.029*x2-0.4459*x3-0.0005*x4)+x3*(-0.2754*x1+0.0248*x2-0.3921*x3+0.0004*x4)+(x4*(0.003*x1-0.0012*x2+0.0003*x3-0.0833*x4))<=-K*(.5*x1.^2+x2.^2+x3.^2+x4.^2)

now how can I solve it and reach K?

[Walter Roberson]

You are missing two ) in defining cond5 .

Count brackets as you go. Start with 0. Every time you encounter a '(', increase your count by 1. Every time you encounter a ')', decrease your count by 1. At the end of the line you will find that you are at count 2, indicating you had two '(' that have no matching ')'

Answer 1

[azam ghamari]

yes, I solve that problem now but it gives me this:

ans =

Empty sym: 0-by-1

and what about the second part of my problem?

thanks

Answer 2

[azam ghamari]

Actually I don't get result, and I wonder why nobody helps me/answer me on this question? I will be thankful if anybody can help me to reach the result.

thanks

[Walter Roberson]

None of us know what the proper place of the two missing ) is.

MATLAB struggles with inequalities.

Also, most of the time when it does find a solution, it just displays a nominal solution -- a point that satisfies the conditions, rather than representing the collection of points that satisfy the conditions. I have posted in the past as to how it chooses the representative point when it internally knows the boundaries.