You may want to review simplifying rational functions first.

As with fractions, it's easy to add or subtract rational
functions with the same denominator. You just add or subtract the
numerators, which are just polynomials. The denominator stays the
same. For example, to compute (−*x*^{3} +
2*x*^{2})/(*x*^{2} − 1) −
(−*x*^{2} − 1)/(*x*^{2}
− 1), we just subtract the numerators, getting
−*x*^{3} + 3*x*^{2} + 1. Then the
answer is (−*x*^{3} + 3*x*^{2} +
1)/(*x*^{2} − 1). (We would have to reduce
this, but the numerator and denominator have no factors in common,
so there's nothing to reduce.)