Amass weighing 4 lb stretches a spring 1.5 in. the mass is given a positive displace-
ment of 2 in from its equilibrium position and released with no initial velocity. assuming that
there is no damping and that the mass is acted on by an external force of 2 cos 3t lb, formulate
the initial value problem describing the motion of the mass (do not solve the resulting system). it's the question about differential equations. provide specific solution.