/10 - 15*b\ |---------| | 2| \ (a - b) / ----------- / 2 \ | 9*b - 4| |---------| \3*b - 3*a/
(10.0 - 15.0*b)*(3.0*b - 3.0*a)/((-4.0 + 9.0*b^2)*(a - b)^2)
(10 - 15*b)*(-3*a + 3*b) ------------------------ / 2\ 2 \-4 + 9*b /*(a - b)
15*(2 - 3*b)*(b - a) -------------------- / 2\ 2 \-4 + 9*b /*(a - b)