Proceed as in Example 4 in Section 11.3 to find a particular solution x(t) of equation (11) in Section 11.3 d?x m- + kx = f(t) (11) dt2 when m = 1, k = 18, and the driving force f(t) is as given. Assume that when f(t) is extended to the negative t-axis in a periodic manner, the resulting function is odd. f(t) = 1 - t, 0