Denominator : getDenom

getDenom takes as argument a rational fraction and returns the denominator of this fraction. Unlike denom, getDenom does not simplify the fraction before extracting the denominator.
Input :

getDenom((x^2-1)/(x-1))

Output :

x-1

Input :

getDenom((x^2+2*x+1)/(x^2-1))

Output :

x^2-1