Some logarithmic functional equations

Vichian Laohakosol; Watcharapon Pimsert; Charinthip Hengkrawit; Bruce Ebanks

Archivum Mathematicum (2012)

  • Volume: 048, Issue: 3, page 173-181
  • ISSN: 0044-8753

Abstract

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The functional equation f ( y - x ) - g ( x y ) = h 1 / x - 1 / y is solved for general solution. The result is then applied to show that the three functional equations f ( x y ) = f ( x ) + f ( y ) , f ( y - x ) - f ( x y ) = f ( 1 / x - 1 / y ) and f ( y - x ) - f ( x ) - f ( y ) = f ( 1 / x - 1 / y ) are equivalent. Finally, twice differentiable solution functions of the functional equation f ( y - x ) - g 1 ( x ) - g 2 ( y ) = h 1 / x - 1 / y are determined.

How to cite

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Laohakosol, Vichian, et al. "Some logarithmic functional equations." Archivum Mathematicum 048.3 (2012): 173-181. <http://eudml.org/doc/247004>.

@article{Laohakosol2012,
abstract = {The functional equation $f(y-x) - g(xy) = h\left(1/x-1/y\right)$ is solved for general solution. The result is then applied to show that the three functional equations $f(xy)=f(x)+f(y)$, $f(y-x)-f(xy)=f(1/x-1/y)$ and $f(y-x)-f(x)-f(y)=f(1/x-1/y)$ are equivalent. Finally, twice differentiable solution functions of the functional equation $f(y-x) - g_1(x)-g_2(y) = h\left(1/x-1/y\right)$ are determined.},
author = {Laohakosol, Vichian, Pimsert, Watcharapon, Hengkrawit, Charinthip, Ebanks, Bruce},
journal = {Archivum Mathematicum},
keywords = {logarithmic functional equation; Pexider equations; logarithmic functional equation; Pexider-type functional equation},
language = {eng},
number = {3},
pages = {173-181},
publisher = {Department of Mathematics, Faculty of Science of Masaryk University, Brno},
title = {Some logarithmic functional equations},
url = {http://eudml.org/doc/247004},
volume = {048},
year = {2012},
}

TY - JOUR
AU - Laohakosol, Vichian
AU - Pimsert, Watcharapon
AU - Hengkrawit, Charinthip
AU - Ebanks, Bruce
TI - Some logarithmic functional equations
JO - Archivum Mathematicum
PY - 2012
PB - Department of Mathematics, Faculty of Science of Masaryk University, Brno
VL - 048
IS - 3
SP - 173
EP - 181
AB - The functional equation $f(y-x) - g(xy) = h\left(1/x-1/y\right)$ is solved for general solution. The result is then applied to show that the three functional equations $f(xy)=f(x)+f(y)$, $f(y-x)-f(xy)=f(1/x-1/y)$ and $f(y-x)-f(x)-f(y)=f(1/x-1/y)$ are equivalent. Finally, twice differentiable solution functions of the functional equation $f(y-x) - g_1(x)-g_2(y) = h\left(1/x-1/y\right)$ are determined.
LA - eng
KW - logarithmic functional equation; Pexider equations; logarithmic functional equation; Pexider-type functional equation
UR - http://eudml.org/doc/247004
ER -

References

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  1. Chung, J.–Y., 10.1016/j.jmaa.2007.02.072, J. Math. Anal. Appl. 336 (2007), 745–748. (2007) Zbl1130.39018MR2348539DOI10.1016/j.jmaa.2007.02.072
  2. Ebanks, B., 10.1007/BF03323552, Result. Math. 42 (2002), 37–41. (2002) Zbl1044.39018MR1934223DOI10.1007/BF03323552
  3. Heuvers, K. J., 10.1007/s000100050112, Aequationes Math. 58 (1999), 260–264. (1999) MR1715396DOI10.1007/s000100050112
  4. Heuvers, K. J., Kannappan, P., 10.1007/s00010-005-2792-8, Aequationes Math. 70 (2005), 117–121. (2005) Zbl1079.39019MR2167989DOI10.1007/s00010-005-2792-8
  5. Kannappan, P., Functional Equations and Inequalities with Applications, Springer, Dordrecht, 2009. (2009) Zbl1178.39032MR2524097
  6. Kuczma, M., An Introduction to the Theory of Functional Equations and Inequalities, second ed., Birkhäuser, Basel, 2009. (2009) Zbl1221.39041MR2467621
  7. Rätz, J., On the theory of functional equation f ( x y ) = f ( x ) + f ( y ) , Elem. Math. 21 (1966), 10–13. (1966) 

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