In each of Problems 23-30, a second-order differential equation and its general solution y(x) are given. Determine the constants A and B so as to find a solution of the differential equation that satisfies the given initial conditions involving y (0) and y' (0).

y" + 2y' - 15y = 0, y(x) = Ae^3x + Be^-5x,

y(0) = 40, y'(0) = -16