Solve Unknown b in Matrix C for No Unique Solutions

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In summary, the conversation discusses finding values of b for which the system of equations y=Cx has no unique solutions. This can be achieved by setting the rank of the matrix C to be less than the number of rows, which can occur when one column is a multiple of another. The system determinant is not directly related to the uniqueness of the solution, but it is used to find the interdependency of the basis.
  • #1
blackbear
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I have the following matrix C =

3 2 1 9
4 2 6 12
1 4 -3 3
0 1 8 (3-b)

y1=[-1 -1 1 -1] transpose

For the vector y, I need to find all values of b such that the system of equations y=Cx has no unique solutions. Can someone help...

Thanks
 
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  • #2
What is the relation between the system determinant and the uniqueness of the solution?
 
  • #3
I am not sure...I thought the system determinant is only used to find the interdependency of the basis. If there exist such a relation as you have mentioned...that is not mentioned in the question; so we can assume anything for the problem.
 
  • #4
By the way in order to have a unique solution r(A), rank equals n. But we know n but I don't know how to get rank!
 
  • #5
Notice how if b = 3 then column 4 becomes a multible of column 1. This solution would make the rank(C) < n = 4 and therefore C would not have an inverse making the system have no unique solitions.
 
  • #6
Thanks Live2Learn...I got it!
 

1. What does it mean when a matrix has no unique solutions?

When a matrix has no unique solutions, it means that there is no single set of values that can satisfy all the equations in the matrix. This could happen if the equations are contradictory or if there are not enough equations to determine a unique solution.

2. How can you solve for an unknown b in a matrix with no unique solutions?

If a matrix has no unique solutions, it is not possible to solve for a specific value of b. However, you can still find a general solution by using techniques like row reduction or Gaussian elimination. This will give you a set of equations that can be satisfied by multiple values of b.

3. Can a matrix have more than one solution for an unknown b?

Yes, a matrix can have multiple solutions for an unknown b. This happens when the equations in the matrix are not enough to uniquely determine a value for b. In this case, there will be an infinite number of solutions that satisfy the equations.

4. Is it possible for a matrix to have no solutions for an unknown b?

Yes, it is possible for a matrix to have no solutions for an unknown b. This can occur when the equations in the matrix are contradictory and cannot be satisfied by any value of b. In this case, the matrix is said to be inconsistent.

5. How does the number of equations in a matrix affect the number of solutions for an unknown b?

The number of equations in a matrix has a direct impact on the number of solutions for an unknown b. If the number of equations is equal to the number of unknowns, there will be a unique solution. If there are more equations than unknowns, there may be no solutions or multiple solutions. And if there are fewer equations than unknowns, there will be an infinite number of solutions.

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