### 2.28.5 Numerator and denominator : `f2nd fxnd`

`f2nd` (or `fxnd`) takes as argument a rational fraction and
returns the liste of the numerator and the denominator of an irreducible
representant of this fraction (see also 2.8.5).

Input :

`f2nd((x``^`

`2-1)/(x-1)) `

Output :

`[x+1,1]`

Input :

`f2nd((x``^`

`2+2*x+1)/(x``^`

`2-1)) `

Output :

`[x+1,x-1]`