Services & Resources / Wolfram Forums
-----
 /
MathGroup Archive
1993
*January
*February
*March
*April
*May
*June
*July
*August
*September
*October
*November
*December
*Archive Index
*Ask about this page
*Print this page
*Give us feedback
*Sign up for the Wolfram Insider

MathGroup Archive 1993

[Date Index] [Thread Index] [Author Index]

Search the Archive

[no subject]

  • To: mathgroup at yoda.physics.unc.edu
  • From: sergio at shark.inst.bnl.gov (Sergio Rescia)
  • Date: Tue, 28 Sep 93 15:20:47 EDT
  • Sender: Sergio.Rescia.Phone:516-282-4232.FAX:516-282-5773 at shark.inst.bnl.gov

I am trying to use Eliminate to eliminate the unknown y in a system of 2 equations:

In[1]:= Eliminate[{ (x-a)^2+(y-b)^2==r^2 , 
                    x^2+y^2==9 },            {y}]

           4    2           2      2
Out[1]= r  + r  (-18 - 2 a  - 2 b  + 4 a x) == 
 
               2    4       2      2  2    4               3          2
>    -81 - 18 a  - a  + 18 b  - 2 a  b  - b  + 36 a x + 4 a  x + 4 a b  x - 
 
         2  2      2  2
>     4 a  x  - 4 b  x


Is there any way to force Eliminate to produce a result in the form:

	expr==0

Or better yet there is any smart way to compute directly the discriminant of the second degree equation 
(in x) Out[1]?

Thank you.

Sergio rescia





  • Prev by Date: Help: how to disp. 3-D vectors
  • Next by Date: Matrix ops
  • Previous by thread: Help: how to disp. 3-D vectors
  • Next by thread: Matrix ops