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Student Support Forum: 'Solve returns empty set' topicStudent Support Forum > General > "Solve returns empty set"

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Josh
04/14/12 8:59pm

I've noticed a problem with the Solve function. For some reason, it will return an empty set when solutions exist. I've been having this happen a lot lately both for systems of equations and even just for a single equation where I want to symbolically solve for a variable (my TI-89's Solve function can do it just fine).

This is the example I ran into today:

In[104]:= Clear[K1, vIN, vOUT, VT, RS, iDS]

Solve[{K1/2*(vIN - (vOUT) - VT)^2 == iDS, vOUT == iDS*RS}, iDS]

Out[105]= {}

However, if I manually substitute iDS*RS for vOUT:

Solve[{K1/2*(vIN - (iDS*RS) - VT)^2 == iDS}, iDS]

Then I get the correct answer. Is there something I'm doing wrong here? Thanks for your help!

Mathematica 8.0.1.0 on Linux x86_64.

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Subject (listing for 'Solve returns empty set')
Author Date Posted
Solve returns empty set Josh 04/14/12 8:59pm
Re: Solve returns empty set Forum Modera... 04/16/12 10:51am
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