Strange simultaneous eqution problem?

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Discussion Overview

The discussion revolves around solving a system of simultaneous linear equations in three variables, specifically focusing on finding solutions in terms of a parameter \( k \) and identifying the values of \( k \) for which the solution is not valid. The scope includes methods of solving linear equations, such as elimination and matrix approaches.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant expresses confusion and requests help with the problem involving the equations: \( x+y+kz=4 \), \( x-2y-z=1 \), and \( kx+7y+5z=10 \).
  • Another participant suggests that the problem is typical and discusses various methods to solve simultaneous equations, including elimination, matrix methods, and Cayley's method, emphasizing the importance of identifying when divisions by zero occur or when a matrix lacks an inverse.
  • A request for a demonstration of the elimination method is made by a participant, indicating interest in practical application.
  • Another participant suggests using elementary row operations to achieve triangular form and inquires about the course of study related to the problem.
  • A link to a resource on Gaussian elimination is provided, along with a claim that there are two specific values of \( z \) that lead to no solution, hinting at a quadratic equation's involvement.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method to solve the equations, and there are varying opinions on the nature of the problem and its complexity.

Contextual Notes

There is uncertainty regarding the specific values of \( k \) that invalidate the solution, and the discussion includes multiple approaches without resolving which is the most effective or correct.

smileandbehappy
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I have a few of these to do so would appretiate if someone could explain this to me as i am stumped.

Find in terms of k a solution to the equations,

x+y+kz=4
x-2y-z=1
kx+7y+5z=10

For what values of k is this solution not valid?

Man thanks in advance for any help given.
 
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smileandbehappy said:
I have a few of these to do so would appretiate if someone could explain this to me as i am stumped.

Find in terms of k a solution to the equations,

x+y+kz=4
x-2y-z=1
kx+7y+5z=10

For what values of k is this solution not valid?

Man thanks in advance for any help given.
Doesn't look strange to me, looks like a fairly typical problem.

How you would do it depends upon how you want to solve simultaneous linear equations! Some people might eliminate one variable at a time. If you do it that way, you will want to keep track divisions by a quantity involving k. For what values of k would you be dividing by 0? Others might set it up as a matrix equation and find the inverse of the coefficient matrix. For what values of k does that matrix not have an inverse? Still others might use Cayley's method: each solution is a fraction in which the denominator is the determinant formed by the coefficients. For what values of k is that determinant equal to 0? Of course, a little reflection will show you that all of those methods are really the same thing!
 
OK then. Will you show me how to do the elimination method?
 
smileandbehappy said:
OK then. Will you show me how to do the elimination method?

Use elementary row operations, at least to put into, ?triangular form? What course are you studying? If linear algebra, then the system should be easy to solve. You could read about one or two methods from an intermediate algebra book just as well.
 
This link takes you through a 3 x 3 example of elimination:

http://en.wikipedia.org/wiki/Gaussian_elimination

This problem is quite straightforward. There are two values of z (both whole numbers) that result in no solution. The solution to a quadratic equation is involved.
 

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