Question

Consider an undamped spring-mass system with mass 3 kg and a spring which is stretched 1 meter by 5 Newtons. Suppose an oscillating force 3 cos(ωt) is acting on the system. What value of ω causes resonance? For this value of ω, find a formula for x(t), the distance between the weight and equilibrium t seconds after the weight starts at x = 0 at rest