CoefficientArrays

CoefficientArrays[polys, vars] gives the arrays of coefficients of the variables vars in the polynomials polys.

Examples

CoefficientArrays[{a x + b y, c x + d y}, {x, y}]
(* {{0, 0}, {{a, b}, {c, d}}} *)

CoefficientArrays[x^2 + 2 x + 1, x]
(* {1, {2}, {{1}}} *)

Please visit the official Wolfram Language Reference for more details.