while (rdeg >= bdeg) {
ex term, rcoeff = r.coeff(*x, rdeg);
if (!divide_in_z(rcoeff, blcoeff, term, var+1))
break;
term = (term * power(*x, rdeg - bdeg)).expand();
while (rdeg >= bdeg) {
ex term, rcoeff = r.coeff(*x, rdeg);
if (!divide_in_z(rcoeff, blcoeff, term, var+1))
break;
term = (term * power(*x, rdeg - bdeg)).expand();