A mass on a frictionless table is attached to a spring with a spring with spring constant k-1 which is itself attached to another spring with spring

A mass on a frictionless table is attached to a spring with a spring with spring constant k-1 which is itself attached to another spring with spring constant k-2. Find an expression for the block's oscillation frequency f in terms of the frequencies f_1 and f_2 at which it would oscillate if attached to spring 1 or spring 2 alone.