Numerator after simplification : numer

numer takes as argument a rational fraction and returns the numerator of an irreducible representant of this fraction (see also 1.8.3).
Input :

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

Output :

x+1

Input :

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

Output :

x+1