Let A be an n x n (square) matrix and let x and y be vectors in all real numbers. Show that if Ax=Ay and x does not equal y, then the matrix A must be singular.

How do I start on this problem?

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- Sep 15th 2010, 05:22 PMguyonfire89Singular Matrices Theorem
Let A be an n x n (square) matrix and let x and y be vectors in all real numbers. Show that if Ax=Ay and x does not equal y, then the matrix A must be singular.

How do I start on this problem? - Sep 15th 2010, 05:23 PMAckbeet
What have you tried so far? I would probably do a proof by contradiction.

- Sep 15th 2010, 05:32 PMguyonfire89
That's the problem, I never learned how to prove a matrix is nonsingular or singular. I know what they mean, that they have an inverse or don't.

Are you saying that I should try to show that it has an inverse? Or can I just do this by trying to find a determinate which is zero? - Sep 16th 2010, 01:53 AMAckbeet
I'm asking what you could do if the matrix had an inverse. Take a look at your equation there.