/ 2 2 \ a*\b - a + a*(a + b)/ ----------------------- / 2 2\ (a + b)*\b - a /
a*(b^2 - a^2 + a*(a + b))/((a + b)*(b^2 - a^2))
/ 2 2\ 2 a*\b - a / + a *(a + b) ------------------------ / 2 2\ (a + b)*\b - a /
(a*(b^2 - a^2) + a^2*(a + b))/((a + b)*(b^2 - a^2))