674 Laplace transforms
̃x(s) =1
s^2
+a^2̃x(s)
s^2. (D.19)
Solving this for ̃x(s), we obtain
̃x(s) =1
s^2 −a^2, (D.20)
and, as we have already shown, the inverse Laplace transform of ̃x(s), which gives us
the solutionx(t) is
x(t) =1
asinh(at). (D.21)