Finding the value of a variable in a matrix

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Homework Help Overview

The discussion revolves around a system of linear equations involving three variables (x, y, z) and a parameter (a). Participants are tasked with determining the value of a that influences the number of solutions to the system, specifically exploring conditions for many solutions, no solutions, and exactly one solution.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the implications of the reduced matrix obtained from the system of equations and question the next steps. Some suggest using an augmented matrix to incorporate the constants from the equations. Others propose alternative methods, such as manipulating the equations directly without matrices, to derive relationships between the variables and the parameter a.

Discussion Status

The discussion is active, with participants exploring different methods to analyze the system of equations. Some guidance has been offered regarding the setup of the augmented matrix and the manipulation of equations, but there is no explicit consensus on a single approach or solution yet.

Contextual Notes

Participants are working under the constraints of a homework assignment, which requires them to explain their reasoning for the values of a that lead to different types of solutions. There is an emphasis on understanding the conditions rather than simply calculating values.

incxx
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Homework Statement


Given :

 x+y+5z = 2

 x+2y+7z = 1

 2x−y+4z = a
.
a) Determine the value of a which will make the given system have many solutions. Explain your answer.
b) Choose a value of a which will make the given system have NO solutions. Explain your answer.
c) Is it possible to choose a value of a, which will make the given system have exactly one solutions? Explain
your answer.

Homework Equations

The Attempt at a Solution


I found the reduced matrix of the system of equations and got,
1 0 3
0 1 2
0 0 0
, but am not sure on what to do next.
 
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incxx said:

Homework Statement


Given :

 x+y+5z = 2

 x+2y+7z = 1

 2x−y+4z = a
.
a) Determine the value of a which will make the given system have many solutions. Explain your answer.
b) Choose a value of a which will make the given system have NO solutions. Explain your answer.
c) Is it possible to choose a value of a, which will make the given system have exactly one solutions? Explain
your answer.

Homework Equations

The Attempt at a Solution


I found the reduced matrix of the system of equations and got,
1 0 3
0 1 2
0 0 0
, but am not sure on what to do next.
You need to set up an augmented matrix whose fourth column contains the constants on the right sides of your equations.
 
Equivalently, don't use matrices at all!
You have:
x+y+5z = 2
 x+2y+7z = 1
 2x−y+4z = a

Subtract the first equation from the second to get y+ 2z= -1.
Subtract the third equation from twice the first equation to get 3y+ 6z= 4- a

Subtract three times the first of those equations from the second to get 0= 7- a.

For what value of a is that true? So for what value of a does the original set of equations have an infinite number or solutions? For what values of a does it have no solution?
 
thank you I understand how to do it now!
 

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