Determine if {(x,y) : x - y = 1} is a subspace of vector space V = R² 6. (15pts) Determine whether S = {1-1,2t +31²,12-21³,2+1³) is a basis for P3. 7. (15pts) Let A be diagonalizable n x n matrix and let P be an invertible n x n matrix suc form of A.Prove that Ak = PBKP-1, where k is a positive integer. Q (15ptr) Prove that if u and y are vectors in R" then my=+y||²||n-y||²