MATLAB: Discrete equation with two unknown variables

discrete equations

[EDIT: 20110523 16:16 CDT – clarify – WDR]
Hi,
I am looking for a simple way to find out the solution for this equation:
y1 = a*x1/(1+b)*x1
y2 = a*x2/(1/b)*x2
a and b are unkown but x1, x2, y1, y2 are known. I need discrete solutions for this equation and not 1 and 0 as solution. How can I compute this in MatLab, I know it is rather simple by head, but I have been cracking my head over this for several days and never am sure of what I find is right.

Best Answer

This can be rewritten as:
a*x1^2 - b*y1 = y1
a*x2^2 - b*y2 = y2
or in matrix form:
A * [a b]' = [y1 y2]'
where:
A = [x1^2 -y1; x2^2 -y2];
So:
x1 = 2;
x2 = 3.3;
y1 = 9;
y2 = 2.9;
A = [x1^2 -y1; x2^2 -y2];
RHS = [y1 y1]';
solution = A\RHS;
a = solution(1);
b = solution(2);
HTH,
Arnaud
Related Question