Arithmetic and polynomials

Polynomials are represented by expressions or by list of coefficients by decreasing power order. In the first case, for instructions requiring a main variable (like extended gcd computations), the variable used by default is x if not specified. For modular coefficients in $\mathbb {Z}$/n$\mathbb {Z}$, use % n for each coefficient of the list or apply it to the expression defining the polynomial.