1.28 For each, decide if it is a vector space; the intended operations are the natural ones. (a) The diagonal 2x2 matrices 0 b [ a, bER} (b) This set of 2 x 2 matrices X xty [x, y ER} xty y (c) This set X ERA | x + y + z+ w=1} Z W (d) The set of functions { f: R - R | df/ dx + 2f = 0} (e) The set of functions { f: R - R | df/ dx + 2f = 1}