SOLUTION: A student says that the system consisting of x=0, y=0, and z=0 has no solutions. Explain the student's error. Write and solve a system.

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Question 270365: A student says that the system consisting of x=0, y=0, and z=0 has no solutions. Explain the student's error. Write and solve a system.
Found 2 solutions by solver91311, Edwin McCravy:
Answer by solver91311(24713)   (Show Source): You can put this solution on YOUR website!


Of course the system has a solution, namely the ordered triple (0, 0, 0)

Nothing to write. The system is already written, namely:

x=0, y=0, and z=0

These are the equations of the three coordinate axes in


John


Answer by Edwin McCravy(20060)   (Show Source): You can put this solution on YOUR website!

The student's error is that 0 is a number,
and therefore is a perfectly good answer.

This system



We can eliminate y by adding the first two equations
just as they are:

 x + y + z = 0
 x - y + z = 0
 -------------
2x     +2z = 0 

We can eliminate y and z by adding the last two equations:

 x - y + z = 0
 x + y - z = 0
 -------------
2x         = 0

So we have the system:



Solve the second one for s, 

2x = 0
 x = 0

Substitute in 

 2x  + 2z = 0
2(0) + 2z = 0
       2z = 0
        z = 0

Substitute in one of the original equations:

x + y + z = 0
0 + y + 0 = 0
        y = 0

Edwin

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