comDenom takes as argument a sum of rational fractions.

comDenom rewrite the sum as a unique rational fraction.
The denominator of this rational fraction is the common denominator of the
rational fractions given as argument.

Input :

comDenom(x-1/(x-1)-1/(x

`^`

2-1))Output :

(x

`^`

3+-2*x-2)/(x`^`

2-1)