Matrices Proof> C=A-B, if Ax=Bx where x is nonzero, show C is singular

In summary, a matrix proof is a mathematical method that uses operations and properties to show the validity of a statement involving matrices. A matrix is considered singular if its determinant is equal to zero, meaning it is not invertible. To prove that a matrix C is singular, we can use the equations Ax=Bx and C=A-B, assuming that x is nonzero. This proof can be extended to matrices of any size, as long as the equations hold true.
  • #1
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Homework Statement


Let A and B be n x n matrices and let C= A - B.
Show that if Ax=Bx, and x does not equal zero, then C must be singular.


Homework Equations





The Attempt at a Solution


Ax-Bx=0
x(A-B)=0
x(C)=0
So, Cx=0

Does that mean C is singular?
 
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  • #2
If Cx=0 and x is not the zero vector, then what would C^(-1)(0) be? C0=0 as well. Would it be x or 0? Sure, it means C is singular.
 

1. What is a matrix proof?

A matrix proof is a mathematical method used to show the validity or truth of a statement involving matrices. It involves using mathematical operations and properties to manipulate matrices and arrive at a conclusion.

2. What does it mean for a matrix to be singular?

A matrix is considered singular if its determinant is equal to zero. This means that the matrix is not invertible and does not have a unique solution.

3. How do you prove that C is singular if Ax=Bx and C=A-B?

To prove that C is singular, we can use the fact that Ax=Bx to substitute for A and B in the equation C=A-B. This will give us the equation C=0, which means that the determinant of C is equal to zero. Therefore, C is singular.

4. Why is it important for x to be nonzero in this proof?

If x is equal to zero, then the equation Ax=Bx becomes 0=0, which does not provide any useful information. By assuming that x is nonzero, we can manipulate the equations to prove that C is singular.

5. Can this proof be extended to matrices of any size?

Yes, this proof can be extended to matrices of any size. As long as the equations Ax=Bx and C=A-B hold true, then it can be proven that C is singular.

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