Find the motion of a mass-spring system having a mass of 0.125 kg, no damping, a spring constant of 1.125 N/m, and a driving force of cos(t)-4sin(t) N. Assume zero initial displacement and velocity.

You need to use this system for a particular application in a fragile environment. You need to change the frequency of the driving force for this application. 

For what frequency of the driving force would the system goes into resonance?