A fast insight into the nonlinear oscillators with coordinate-dependent mass

The nonlinear oscillators with coordinate dependent mass is studied by Ren (Results in Physics, 2018(11):1052–1053) and Wu (Results in Physics, 2018(10):270–271) respectively. In this letter, He’s frequency-amplitude formulation combined with the average residuals is used to study this problem. The results of this letter reveal that this method is simple and effective, and is expected to open up some new perspectives for the study of the nonlinear oscillators theory