# XSOLVE -- solve ax + by = c
  #
  # xsolve(a,b,c) returns a solution of ax + by = c.
  #
  # assume that the gcd of a and b divides c,
  # where a, b, c are integers.
  #


     xsolve := proc(a,b,c)
        local r, q, s, u, x;
        r := a mod b;
        if r = 0 
          then RETURN( [0,c/b] );
             else 
                s := xsolve( b, r, c );
                u := s[1]; x := s[2];
                q := (a-r)/b;
                RETURN( [ x, u - q*x ] );
            fi;
     end:

  # jac, 6/11/2001