Published online by Cambridge University Press: 30 August 2018
In this paper, we consider the Diophantine equations
The first author was supported by NSF of China (No. 11601476) and the Guangdong Provincial Natural Science Foundation (No. 2016A030313013 ) and Foundation for Distinguished Young Teacher in Higher Education of Guangdong, China (YQ2015167). The second author thanks Purdue University Northwest for support.