Matrix A and Vectors b & c in R^3: Solving Ax=b & Ax=c

In summary, to construct a 3x3 matrix A and vectors b and c in R^3 so that Ax=b has a solution but Ax=c, the matrix A should be singular and the vector b should be the only vector for which Ax=b has a solution. The simplest and most natural way to do this is to use a singular 3x3 matrix A and choose vector b accordingly.
  • #1
Jen2114
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Homework Statement


Construct a 3x3 matrix A and vectors b and c in R^3 so that Ax=b has a solution but Ax=c

Homework Equations

The Attempt at a Solution


So I don't know where to start. I am not sure if the problem is asking me to create a matrix with real numbers or variables. What I do know is that Ax=b has a solution if each row has a pivot , except the last column. So How would I use this to answer the question?
 
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  • #2
You left off a "doesn't" at the end of the question.

Taking that as read, the matrix has to be singular, otherwise we can just left-multiply both sides by ##A^{-1}## to find solutions for both equations.

What is the simplest, most monotonous, singular, 3 x 3 matrix you can think of?

If you call that matrix A, what is the only vector b for which A x = b will have a solution x?

I suspect that may not be the matrix they are looking for, but that's the simplest and most natural answer to the question as posed.
 
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  • #3
Ok thank you for your help
 

What is a matrix A and vectors b & c in R^3?

A matrix A is a rectangular array of numbers or symbols that is often used to represent a system of linear equations. Vectors b and c are ordered sets of numbers or symbols that can be represented as columns in a matrix. In R^3, these vectors have three components and can be visualized as points in three-dimensional space.

How do you solve the equations Ax=b and Ax=c?

To solve these equations, you can use the method of Gaussian elimination or matrix inversion. In Gaussian elimination, you manipulate the matrix A through a series of row operations to reduce it to an upper triangular form. Then, back substitution is used to solve for the variables in the equations. In matrix inversion, you find the inverse of A and multiply it by the vector b or c to find the solution.

What does it mean to solve Ax=b and Ax=c?

Solving these equations means finding the values of the variables that make the equations true. In other words, you are finding the point(s) where the lines or planes represented by the equations intersect in three-dimensional space.

What if the equations Ax=b and Ax=c have no solution?

If the equations have no solution, it means that the lines or planes represented by the equations do not intersect in three-dimensional space. This could indicate that the system is inconsistent or that there is an error in the equations.

Can the equations Ax=b and Ax=c have more than one solution?

Yes, the equations can have infinitely many solutions if the lines or planes represented by the equations are parallel. In this case, the equations are dependent and the solution set forms a line or a plane in three-dimensional space.

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