How can I solve the linear system of equations with Matlab?

Hi everyone, I want to find a function to solve the linear system of equations n Matlab. For example, let's focus on this system of equations: x1+x2+2x3=0 x1+2x2-x3=0

Suppose that the answer is: x1=-a, x2=5a, x3=a. I want Matlab to show [-1 5 1]'

How can I do that? Please help me. Your help will be really appreciated. Thank you.

Answer 1

[Azzi Abdelmalek]

a=1;  
x1=-a,
x2=5a,
x3=a
sol=[x1 x2 x3]

[Nghia]

But I want when I enter the system of equation, it will show the [-1 5 1].

[Azzi Abdelmalek]

I don't understand what you want. Please reformulate your question and make it clear

Answer 2

[Roger Stafford]

If your equations are homogeneous as in your example, you need to use matlab's 'null' function. See its documentation at:

 http://www.mathworks.com/help/matlab/ref/null.html

In your example its solution would be

 Z = null([1 1 2;1 2 -1]);

and the column vector Z would only be proportional to [-1 5 1] since it will have a norm of one.