a) \( D_f = (-\infty, -2) \cup (-2, 2) \cup (2, \infty) \)
b) \( D_g = (-\infty, -3\rangle \cup \langle 3, \infty) \)
c) \( D_h = \langle \frac{1}{2}, \infty) \)
d) \( D_k = (-\infty, -3) \cup (-3, 5\rangle \)
e) \( D_m = (0, \infty) \)
f) \( D_f = (1, 3) \cup (3, \infty) \)