Re: Using Solve[] - What did I do wrong?

• To: mathgroup at smc.vnet.net
• Subject: [mg109316] Re: Using Solve[] - What did I do wrong?
• From: Simon Pearce <Simon.Pearce at nottingham.ac.uk>
• Date: Wed, 21 Apr 2010 07:47:20 -0400 (EDT)
• References: <201004210830.EAA26548@smc.vnet.net>

```Hi,

You have four equations and effectively wish to solve for 5 variables,
which Solve can't manage to do so it returns an  empty solution set. If
you only tell it to eliminate three of the four d variables then you get
a solution which includes the last one.

Simon

-----Original Message-----
From: eric948470 [mailto:eric948470 at gmail.com]
Sent: 21 April 2010 09:31
To: mathgroup at smc.vnet.net
Subject: [mg109316] [mg109305] Using Solve[] - What did I do wrong?

Hi,

If you look at the command below, you would probably be able to
understand what I was trying to do. I have linear equations, and I
want to solve for the variable g2, and I don't want the variables dx1,
dx2, dy1 and dy2 in the answer. What I get for the output is {{}}.
What did I do wrong?

Solve[{phi2 + a2*dx1 + b2*dy1 + c2*dx2 + d2*dy2 == 0,
psi2 + A2*dx1 + B2*dy1 + c2*dx2 + D2*dy2 == 0, dx2 == -g2 - =
f2*dy2,
dx1 == -g1 - f1*dy1}, g2, {dx1, dx2, dy1, dy2}]

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