Which of the following are vector spaces? Justify your answer!
(a) The set of all row vectors of the form (a, 3a).
(b) The set of all vectors of the form (a, a + 1).
(c) The set of all continuous functions for which f(- 1)= 0.
(d) The set of all periodic functions of period 1, i.e., f(x + 1) = f(x).
(e) The set of all non-negative functions: f(x) ≥ 0.
(f) The set of all even polynomials: p(x) = p(-x).
(g) The set of all polynomials p(x) that have x - 1 as a factor.
(h) The set of all quadratic forms q(x, y) = ax2 + bxy + cy2.