How to take the positive root for system of equations?

[rskibba]

I need to solve the equations for X,Y and Z.  My current issue is I need a single equiation for each to solve the system.  What is happening is I end up with a  +/- solution due to the radical in the denominator.  So how do I get MathCAD to use just the positive value and solve for all three variables?

[ValeryOchkov]

I hope You will understand why You have no solution

[rskibba]

Valery,

Thanks for the response. OK I get it. I think the question I am really trying to answer is given the partial derivative of S on my attached script, How can I symbolically solve for X,Y, and Z?

Thanks,

Richard

[LucMeekes]

With something like this:

Success!
Luc

[rskibba]

Luc,

Thanks for responding.  I tried that and basically it does not come back with an answer.  But if I solve just one of the variables X,Y, or Z.  It comes back with a +/- result.  This leads me to believe that the radical is causing problems. My goal is to come up with a general solution that I can use for a comparison.

[ValeryOchkov]

richard skibba написал(а):

How can I symbolically solve for X,Y, and Z?

Thanks,

Richard

Why do you need it?

[LucMeekes]

You can't.

I'll demonstrate it on a simpler example. Given:

Please indicate the positive results for x, y and z.

Success!
Luc