Let y(x) satisfy the ordinary differential equation
d^2y/dx^2 - (a^2)y = f(x)
where a>0, and y(x) tends rapidly to zero as x tends to +/- ∞. Show that the Fourier transform ŷ(k) of y(x) is given by
ŷ(k) = - f^(k)/(k^2+a^2)
(in the line above f^(k) is supposed to be f-hat(k), sorry couldn't find the right symbol)