Extended gcd

Returns the final results of the extended Euclidean algorithm: an extension to the Euclidean algorithm which computes, besides the greatest common divisor of polynomials p and q, the coefficients of Bézout's identity, which are polynomials r and s such that p asterisk times r plus q asterisk times s equals g c d left parenthesis p comma q right parenthesis

extended_gcd(Polynomials, Polynomials)

Given two polynomials p and q, returns a vector with three elements: the first one is the greatest common divisor of p and q, the second and the third ones are r and s, with the notation used above.