y^(4) + 18y'' + 81y = 0 Find the general solution of the differential equation
Follow Math Help Forum on Facebook and Google+
your cahracteristic eqn is L^4 + 18L^2 + 81 = 0 (L^2 +9)^2 = 0 L = 3i (recall you only need one root) so you solutions are cos(3x),sin(3x),xcos(3x), and xsin(3x)
View Tag Cloud