Question

Suppose that A is nxn. Show that ||Ax|| = ||A^Tx|| if and only if AA^T = A^TA. Cite any theorems or definitions used.

A^T represents A transpose.

Answer 1

||Ax|| means the length or magnitude of Ax?

Answer 2

Yup

Answer 3

And the if and only if means that we have to prove both ways

Answer 4

Yep. what's x?

Answer 5

just a variable

Answer 6

Okay. I'll try and see what I can do.

Answer 7

I don't think I an around there. Maybe not now.

Answer 8

If I ever got an idea, I would post it here.

Answer 9

okay thanks for the help tho
... youve already taken linear algebra?