Quadratic Equation with three variables

Click For Summary

Discussion Overview

The discussion revolves around the nature of quadratic equations involving three variables and their geometric interpretations, particularly in relation to conic sections and quadric surfaces. Participants explore whether a quadratic equation in three variables can be seen as representing a complete cone or if it describes other geometric forms.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants propose that a quadratic equation of three variables could represent a complete cone, drawing parallels to the representation of conic sections in two variables.
  • Others question whether having three independent variables still qualifies as a quadratic equation.
  • A participant cites examples of quadratic equations in three variables, suggesting that they represent quadric surfaces rather than a complete cone.
  • It is noted that a second-degree equation in three variables can represent various forms, including spheres, ellipsoids, paraboloids, hyperboloids, and cones, indicating a broader classification than just a complete cone.
  • One participant expresses frustration with another's questions, suggesting that they should conduct more research on the topic.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether a quadratic equation in three variables represents a complete cone, with multiple competing views presented regarding the nature of such equations and their geometric interpretations.

Contextual Notes

The discussion includes varying interpretations of terminology such as "quadratic equation" and "quadric surface," which may depend on specific definitions and contexts. There are also unresolved questions about the implications of having independent variables in quadratic equations.

Leo Authersh
If a quadratic equation of two variables represents a conic section (planar intersection of a cone), then does a quadratic equation of three variables represent the complete cone?

@fresh_42 @FactChecker @WWGD
 
Mathematics news on Phys.org
If you have 3 independent variables, is it still a quadratic equation?
 
Leo Authersh said:
If a quadratic equation of two variables represents a conic section (planar intersection of a cone), then does a quadratic equation of three variables represent the complete cone?
No.
The usual terminology is second-degree equation. As already mentioned, a second-degree equation in three variables represents a quadric surface, including spheres, ellipsoids, paraboloids, hyperboloids, cones, and a few other degenerate surfaces (the equation ##x^2 + y^2 + z^2 = 0## represents a single point at the origin.)

@Leo Authersh, please do a little basic research before posting your questions. Also, I have moved several of your threads to the General Math section. They are not questions that pertain to Topology or Analysis.
 
  • Like
Likes   Reactions: Leo Authersh

Similar threads

  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 16 ·
Replies
16
Views
5K
  • · Replies 19 ·
Replies
19
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 11 ·
Replies
11
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K