where and are both integer polynomials. Functional congruences are sometimes also called "identical congruences" (Nagell 1951, p. 74).
Functional Congruence
See also
CongruenceExplore with Wolfram|Alpha
References
Nagell, T. "Algebraic Congruences and Functional Congruences." §22 in Introduction to Number Theory. New York: Wiley, pp. 73-76, 1951.Referenced on Wolfram|Alpha
Functional CongruenceCite this as:
Weisstein, Eric W. "Functional Congruence." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/FunctionalCongruence.html