Answer to Question #41427 in Calculus for FullOfWonder

Question

The diameter of a cat's pupil is given by f(x) = (160x^-0.4 + 90)/(4x^-0.4+15) where x is the intensity of light on the pupils.
1. By considering lim as x tends to infinity of f(x), determine the diameter of the cat's pupils due to very intense light.
2. Show that f(x) may be written as f(x)=(160+90x^0.4)/(4+15^0.4)
3. Deduce the diameter of the cat's pupil for as light diminishes to a minimum intensity.