Re: FindInstance puzzler

• To: mathgroup at smc.vnet.net
• Subject: [mg83696] Re: [mg83633] FindInstance puzzler
• From: Andrzej Kozlowski <akoz at mimuw.edu.pl>
• Date: Wed, 28 Nov 2007 05:41:04 -0500 (EST)
• References: <200711260849.DAA29897@smc.vnet.net> <55F7C11F-CAB8-47B4-AE40-DA470C74C8C1@mimuw.edu.pl> <474AF639.50705@wolfram.com> <52B4543A-8103-4C24-9786-8C554D247748@mimuw.edu.pl>

```On 27 Nov 2007, at 17:05, Andrzej Kozlowski wrote:

> Reduce[2*y*I*Sqrt[x] + 2*(y - I*Sqrt[x]) == 0, {x, y}, Reals]

This should have been:

In[17]:= Reduce[2*y*I*Sqrt[x] + 2*(y - y*I*Sqrt[x]) == 0,
{x, y}, Reals]
During evaluation of In[17]:= Reduce::nddc:The system 2 \[ImaginaryI]
Sqrt[x] y+2 (y-\[ImaginaryI] Sqrt[x] y)\[LongEqual]0 contains a
nonreal constant 2 \[ImaginaryI]. With the domain \
[DoubleStruckCapitalR] specified, all constants should be real. >>
Out[17]= Reduce[2*I*Sqrt[x]*y + 2*(y - I*Sqrt[x]*y) == 0,
{x, y}, Reals]

but it other than that it does not change anything. Note that:

Reduce[Simplify[2*y*I*Sqrt[x] + 2*(y - y*I*Sqrt[x]) == 0], {x, y},
Reals]
y==0

What I really mean tto say is: wouldn't it be a litte better to first
automatically apply Simplify in such situation to see if the I's could
be got rid of?

Andrzej Kozlowski

```

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