Show that P is idempotent. I'm very confused on how to prove it. I get stuck on the first step P=(X(X^TX)^-1X^T
It then asks to obtain Eigen values of P given Matrix x. The rows for the matrix is as follows row 1: 1 2 , row 2: 1 4, row 3: 1 1, row 4: 1 3