Can RREF be used for any size matrix?

In summary, the RREF algorithm can be applied to any matrix, regardless of size, to find the solution set of the corresponding system of equations. For a 1x1 matrix representing a single equation, the matrix can be solved directly without using row reduction. For a 2x1 matrix representing a system of two equations in one variable, row reduction can be used but it may not be necessary. The minimum size of a matrix for which RREF makes sense is when it represents a nonhomogeneous system with at least one constant term on the right side of the equations. However, the algorithm itself does not care about the entries or what they represent.
  • #1
Mr Davis 97
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I understand that the RREF algorithm can be used on matrices representing systems of equations to find the solution set of that system. However, can this algorithm be used for any matrix of any size? For example, what if we, what if we had a 1x1 mattix, or a 2x1? What is the minimum size of a matrix for which RREF makes sense?
 
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  • #2
You can always apply the algorithm. The matrix might be in its final form already, then nothing changes.
 
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  • #3
Mr Davis 97 said:
I understand that the RREF algorithm can be used on matrices representing systems of equations to find the solution set of that system. However, can this algorithm be used for any matrix of any size? For example, what if we, what if we had a 1x1 mattix, or a 2x1? What is the minimum size of a matrix for which RREF makes sense?
Think about the system of equations a matrix represents. A 1x1 matrix represents a single equation such as 3x = 0. For an equation like 3x = 6, you would need an augmented 1x2 matrix. You could solve this by row reduction, but it seems like massive overkill.

A 2x1 matrix would represent a system of two equations in one variable, such as
3x = 0
2x = 0
The matrix itself would consist of a single column whose entries are 3 and 2, respectively. Again, you could use row reduction, and find that (surprise!) x = 0. For such simple systems, you could use RREF, but it doesn't make much sense.
 
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Alright, it makes sense. Just one further question. How does a matrix with only one column represent a system of equations? I see that you use zero when you right it out in equation form, but where is that coming from?
 
  • #5
Mr Davis 97 said:
Alright, it makes sense. Just one further question. How does a matrix with only one column represent a system of equations? I see that you use zero when you right it out in equation form, but where is that coming from?
It would represent a homogeneous system, a system of equations where the constant terms are all zero.

So the system of two equations in one unknown
3x = 0
2x = 0
could be represented by this matrix:
##\begin{bmatrix} 3 \\ 2 \end{bmatrix}##

A nonhomogeneous system such as
4x = 10
2x = 4
could be represented by the augmented matrix
##\begin{bmatrix} 4 & | & 10 \\ 2 & | & 4\end{bmatrix}##
I hope it's obvious that this system has no solution.
 
  • #6
Wouldn't ##\begin{bmatrix} 3 & 0 \\ 2 & 0\end{bmatrix}## represent the homogeneous system that you are talking about, and not ##\begin{bmatrix} 3 \\ 2 \end{bmatrix}##?
 
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Mr Davis 97 said:
Wouldn't ##\begin{bmatrix} 3 & 0 \\ 2 & 0\end{bmatrix}## represent the homogeneous system that you are talking about, and not ##\begin{bmatrix} 3 \\ 2 \end{bmatrix}##?

That's what I think too.
 
  • #8
Hey Mr Davis 97.

The algorithm can be applied to an arbitrary matrix since all operations are based on multiplication (scalar multiplication) and addition (and subtraction) which can be done for any set of values.
 
  • #9
This is getting a matter of definitions. The algorithm doesn't really care about what the entries represent.
 
  • #10
Mr Davis 97 said:
Wouldn't ##\begin{bmatrix} 3 & 0 \\ 2 & 0\end{bmatrix}## represent the homogeneous system that you are talking about, and not ##\begin{bmatrix} 3 \\ 2 \end{bmatrix}##?
Math_QED said:
That's what I think too.
Most of the linear algebra books I've seen use the matrix for the coefficients of the variables. If the system is nonhomogeneous (constants on the right sides of the equations, they use an augmented matrix.
If the system of equations is homogeneous, there's no point in dragging along a column of zeroes, none of which can change from any row operations.
 

FAQ: Can RREF be used for any size matrix?

What is RREF and why is it used for all matrices?

RREF stands for "reduced row echelon form" and it is a way to organize a matrix by performing a series of row operations to simplify it into a more useful form. It is used for all matrices because it allows for easier computation of solutions to systems of linear equations and can reveal important information about the matrix such as its rank and nullity.

How do you find the RREF of a matrix?

To find the RREF of a matrix, you must perform a series of row operations such as swapping rows, multiplying rows by a number, and adding or subtracting rows from each other. The goal is to create a matrix where the leading coefficient of each row is 1 and all other entries in the same column are 0. This process can be done by hand or by using a calculator or computer program.

Can any matrix be reduced to RREF?

Yes, any matrix can be reduced to RREF using the appropriate row operations. However, the resulting RREF may not always be unique, as there can be multiple ways to reduce a matrix to its RREF.

How is RREF useful for solving systems of linear equations?

RREF can be used to solve systems of linear equations by organizing the equations into a matrix and then reducing it to its RREF. The RREF can reveal important information about the system, such as whether it has a unique solution, no solution, or infinitely many solutions. It also makes it easier to find the solutions by back-substitution.

What other applications does RREF have in mathematics?

RREF has many applications in mathematics, such as in linear algebra, where it can be used to find the inverse of a matrix and to determine linear independence and dependence of vectors. It is also used in multivariate calculus for optimization problems and in differential equations for solving systems of linear differential equations.

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