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## Homework Statement

Consider a linear system of four equations with three unknowns. We are told that the system has a unique solution. What does the rref of the co efficient matrix look like?

## Homework Equations

## The Attempt at a Solution

When it says "unique solution" I'm going to guess it means it has 1 solution.

Correct me if I'm wrong but, I believe that a system of 3 equations with 3 unknowns that has a unique solution will look like this:

[ 1 0 0 l x

0 1 0 l y

0 0 1 l z]

But for a system that has 4 equations with three unknowns, would it look like this:

[ 1 0 0 l x

0 1 0 l y

0 0 1 l z

0 0 0 l k] ?

This is what gets me, when a row has all 0's it means that it has multiple solutions.

Thanks in advance.