Note on "The derivation of EOQ/EPQ inventory models with two backorders costs using analytic geometry and algebra".

• We show that algebraic methods of Cárdenas-Barrón [2] are questionable. • We provide our improvements for algebraic methods of Cárdenas-Barrón [2]. • We indicate that Sphicas [1] already solved these models by algebraic methods. This study examines the paper of Cárdenas-Barrón, entitled "The derivation of EOQ/EPQ inventory models with two backorders costs using analytic geometry and algebra." that was published in Applied Mathematical Modelling at 2011 to point out it contains questionable results. The algebraic geometry and algebra applied by Cárdenas-Barrón [2] violated the rule of the arithmetic-geometric mean (AGM) mentioned by Cárdenas-Barrón [74]. Moreover, we point out Sphicas [1] had already solved this kind of EOQ and EPQ models using algebraic methods. [ABSTRACT FROM AUTHOR]