The natural frequency of the system shown in Figure is f=1πxkM. The pulleys are smooth and massless. Find x.

If the mass M is displaced by x from its mean position each spring further stretches by 2x.Net restoring force is     F=−8kx⇒Ma=−8kx⇒f=12πax⇒f=12π8kM=1π2kM⇒x=2