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Some logarithmic functional equations

Vichian Laohakosol, Watcharapon Pimsert, Charinthip Hengkrawit, Bruce Ebanks (2012)

Archivum Mathematicum

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.

Some properties of the jacobian sn z function.

István Fenyö (1985)

Stochastica

Using some results of the theory of functional equations we deduce some properties of the Jacobian sn z function which seem to be new. Some functional equations have also been found which are fulfilled by the sn z function which the author did not find in the literature.

Some remarks on a problem of C. Alsina.

J. Matkowski, M. Sablik (1986)

Stochastica

Equation[1] f(x+y) + f (f(x)+f(y)) = f (f(x+f(y)) + f(f(x)+y))has been proposed by C. Alsina in the class of continuous and decreasing involutions of (0,+∞). General solution of [1] is not known yet. Nevertheless we give solutions of the following equations which may be derived from [1]:[2] f(x+1) + f (f(x)+1) = 1,[3] f(2x) + f(2f(x)) = f(2f(x + f(x))).Equation [3] leads to a Cauchy functional equation:[4] phi(f(x)+x) = phi(f(x)) + phi(x),restricted to the graph of the function f,...

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