PolynomialMod

PolynomialMod[poly, m] gives the polynomial poly reduced modulo m.

PolynomialMod[poly, {m1, m2, …}] reduces modulo all of the mi.

Examples

Reduce coefficients modulo:

PolynomialMod[5 x^2 + 7 x + 3, 3]
(* 2 x^2 + x *)

Multiple moduli:

PolynomialMod[12 x^2 + 15 x + 9, {2, 3}]

Please visit the official Wolfram Language Reference for more details.