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>*Reply-to*: jmg336 at nyu.edu*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.