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Need help for a simple equation

• To: mathgroup at smc.vnet.net
• Subject: [mg12813] Need help for a simple equation
• From: Tae-Wan Kim <tae-wan.kim at sdrc.com>
• Date: Fri, 12 Jun 1998 04:05:43 -0400
• Organization: SDRC
• Sender: owner-wri-mathgroup at wolfram.com

Hello,

I need your help to solve a simple equation.

My problem is as follows:
f(x, y) = a x^2 + b xy + c y^2 + d x + e y + f = 0 (1)

partial derivative of f(x,y) with respect to x: dfx(x, y) = 2 a x + b y
+ d = 0 (2)

I'd like to solve (1) and (2) using Mathematica.

I get two set of roots:
(x_0, y_0) and (x_1, y_1) 

I programmed as sollows:
SetAttributes[a, Constant]
SetAttributes[b, Constant]
SetAttributes[c, Constant]
SetAttributes[d, Constant]
SetAttributes[e, Constant]
SetAttributes[f, Constant]
f[x_, y_] := a x^2 + b xy + c y^2 + d x + e y + f

dfx = D[f[x,y], x] 
-> this didn't work

I don't know what to do here.

Could you please tell me Mathematics program to solve this problem?

Thank you.

Best regards,

Tae-wan Kim
SDRC

• Follow-Ups:
  • Re: Need help for a simple equation
    • From: Daniel Lichtblau <danl>