; This Mathomatic input shows how "simplify fraction" and "unfactor fraction" work.
1/x+1/y+1/z
fraction ; Convert expressions with algebraic fractions into a single fraction.
simplify
simplify fraction ; does the same as the above fraction command, but simplifies more.
unfactor ; Expand the products of sums.
unfactor fraction ; Fully expand algebraic fractions by also expanding division of sums.