1 1 -- - -- 2 2 a b ------- / 1 \ |-----| \a - b/
/1 1 \ (a - b)*|-- - --| | 2 2| \a b /
(a - b)*(a^(-2) - 1/b^2)
/ 2 2\ (a - b)*\b - a / ----------------- 2 2 a *b
1 1 a b - + - - -- - -- a b 2 2 b a
/ 3 3 2 2\ -\a + b - a*b - b*a / ------------------------- 2 2 a *b
2 -(a - b) *(a + b) ------------------ 2 2 a *b