In each case, write X as the sum of a vector in U and a vector in U⊥.
(a) X = [2 1 6], U = span{[3 -1 2], [2 0 -3]}
(b) X = [2 0 1 6],
U = span{[l 1 1 1], [ 1 1 -1 -1], [1 -1 1 -1]}
(c) X = [a b c d],
U = span{[l -1 2 0], [-1 1 1 1]}