p1(x) = - 72/40·(x - 40) + 72
--------------------------------------------------
f(x) = a/(x + b) + c
f(40) = 72 --> a/(b + 40) + c = 72
f'(40) = - 72/40 --> - a/(b + 40)^2 = - 9/5
f(10) = 135 --> a/(b + 10) + c = 135
Löse das Gleichungssystem und erhalte: a = 79380 ∧ b = 170 ∧ c = -306
p(x) = 79380 / (x + 170) - 306
--------------------------------------------------
~plot~ -72/40*(x-40)+72;79380/(x+170)-306;{40|72};{10|135};[[-10|100|-20|180]] ~plot~