Re: What is causing this error message?

• To: mathgroup at smc.vnet.net
• Subject: [mg57598] Re: What is causing this error message?
• From: Jean-Marc Gulliet <jeanmarc.gulliet at 9online.fr>
• Date: Wed, 1 Jun 2005 06:04:40 -0400 (EDT)
• Organization: New York University
• References: <d7hake\$3qc\$1@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Bookreader wrote:
> 	NSolve[{x^3y + xy - 10 = 0, xy^2 - xy + 6 = 0}, {x, y}]
>
> 	Set::write: Tag Plus in -10 + x y + x^3  y is Protected. More?
>
> 	Please tell me how to correct this.
>
> 	Thanks.
>
You used the Set operator (single =, which is an assignment) rather than
the Equal (double ==, which is a logical operator) so here Mathematica
tries to assign the value zero to each of the equations, hence the error
message. What you want is

In[1]:=
NSolve[{x^3*y + x*y - 10 == 0, x*y^2 - x*y + 6 == 0}, {x, y}]

Out[1]=
{{x -> 1.38167 + 1.02952*I,
y -> -0.109449 - 1.70695*I},
{x -> 1.38167 - 1.02952*I,
y -> -0.109449 + 1.70695*I},
{x -> -0.510413 + 1.72079*I,
y -> 2.02035 + 1.05397*I},
{x -> -0.510413 - 1.72079*I,
y -> 2.02035 - 1.05397*I}, {x -> -1.74251,
y -> -1.4218}}

Best regards,
/J.M.

```

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