shiluach haken

Question

Dear Rav Abadi Shalom u'vracha Reciently we learned about shiluach haken in masekhet Chulin. It appearent from that Gemora as well as from multiple places in RAMBAM that mitzva shiluach haken is lav hanitak le'ase. please explain to me this concept better, namely is it possible to perform only ase without lo taase in the situation of lav hanitak lease. Thank you very much.