Solve the following differential equations subject to the specified initial conditions
(a) d2v / dt2 + 4v = 12, v(0) = 0, dv(0) / dt = 2
(b) d2i / dt2 + 5 di / dt + 4i = 8, i(0) = -1, di(0) / dt = 0
(c) d2v / dt2 + 2 dv / dt + v = 3, v(0) = 5, dv(0) / dt = 1
(d) d2i / dt2 = 2 di / dt = 5i = 10, i(0) = 4, di(0) / dt = -2