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