Help with Matric proof!

BigDave48

Let A= I - X(X'X)inverseX' to clarify: '=transpose; inverse of quantity (X'X)

1. Must A be a square matrix?
2. Must (X'X) be a square matrix?
3. Must X be a square matrix?
4. Show whether matrix A is an idempotent matrix (i.e. that AA=A)

Thanks.

mathwonk

im so stupid! i cant follow aNY OF THAT. if i could understand the question i could answer it instantly.

BigDave48

Sorry. I really would appreciate some help.

To be more clear: I is an identity matrix

Questions 1,2,and 3 are essentially Yes/No with a provided proof or explanation.

Does this help, clarify?

Thanks.

mathwonk

come on man.

yenchin

What do you mean by
"Let A= I - X(X'X)inverseX' to clarify: '=transpose; inverse of quantity (X'X)"

Sorry but it's incomprehensible.