Solving an inequation of first degree issue

Hello,

i am trying to solve this inequation:

a = 3*x + 21 <= 5*x + 13

the answer matlab is giving me when i use:

solve(a)

is 5. But the answer should be x>= 4. What i am doing wrong here?

Thanks

Answer 1

[John D'Errico]

syms x
a = 3*x + 21 <= 5*x + 13

a = 

asol = solve(a,'returnconditions',true)

asol = struct with fields:
             x: [1×1 sym]
    parameters: [1×1 sym]
    conditions: [1×1 sym]

asol.x

ans = 

x

asol.conditions

ans = 

It looks like x >= 4 is the solution.

When you have a problem with multiple solutions, certainly an inequality like this, you need to tell MATLAB to describe the solution properly. When all I do is use solve on a, what does it do? It gives me AN answer, a valid solution to the problem.

solve(a)

ans = 

5

Read the help docs for solve, where it explains the use of this property.