ON A GENERALIZED UPPER BOUND FOR THE EXPONENTIAL FUNCTION

  • Kim, Seon-Hong (Department of Mathematics, Sookmyung Women's University)
  • Received : 2008.11.17
  • Accepted : 2009.02.02
  • Published : 2009.03.31

Abstract

With the introduction of a new parameter $n{\geq}1$, Kim generalized an upper bound for the exponential function that implies the inequality between the arithmetic and geometric means. By a change of variable, this generalization is equivalent to exp $(\frac{n(x-1)}{n+x-1})\;\leq\;\frac{n-1+x^n}{n}$ for real ${n}\;{\geq}\;1$ and x > 0. In this paper, we show that this inequality is true for real x > 1 - n provided that n is an even integer.

Keywords

References

  1. G. H. Hardy, J. E. Littlewood, G. Polya, Inequalities, Cambridge, 1975.
  2. J. Karamata, Sur l'approximation de $e^{x}$ par des fonctions rationnelles (in Serbian), Bull. Soc. Math. Phys. Serbie, 1 (1949), 7-19.
  3. S.-H. Kim, Densely algebraic bounds for the exponential function, Proc. Amer. Math. Soc. 135 (2007), 237-241. https://doi.org/10.1090/S0002-9939-06-08452-8
  4. W. E. Sewell, Some inequalities connected with exponential function (in Spanish) Rev. Ci (Lima), 40 (1938), 453-456.
  5. J. E. Wetzel, On the functional inequality f(x + y) ${\ge}$ f(x) f(y), Amer. Math. Monthly 74 (1967), 1065-1068. https://doi.org/10.2307/2313604