Rational functions.

The distance that separates the image from the lens of a camera can be modeled by the function D(d)= 5d/d-5,

where D is the distance between the image and the lens, in centimeters, and d is the distance between the subject photographed and the lens, in centimeters. For a photograph to be in focus, the distance between the lens and the sensor must be equal to the distance from the lens to the image. It is possible to adjust the distance between the sensor and the lens.

a) Represent graphically the function