Abstract
In this paper, we give a new proof using Newton polygons for an irreducibility criterion established by Singh and Kumar. Then we prove a conjecture of Koley and Reddy. In addition, we give a new proof for the statement that with is irreducible unless , which is a conjecture of Harrington.
Acknowledgments
We would like to thank the referees for detailed comments. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches.