For each, list three elements and then show it is a vector space. (a) The set of

Question:

For each, list three elements and then show it is a vector space.
(a) The set of 2 × 2 matrices with real entries under the usual matrix operations.
(b) The set of 2 × 2 matrices with real entries where the 2, 1 entry is zero, under the usual matrix operations.