determine the approximate instantaneos rate of change in the intensity of light at exactly 3m from flash bulb.

Question

A photographer uses a light meter to measure the intensity of light from a flash bulb. The intensity for the flash bulb,I, in lux, is a function of the distance from the light, d, in meters, and can be represented by I(d)=10/d^2, d>0

Answer 1

To approximate the instantaneous rate of change, you want a very small interval around d=3, such as d = 2.9 and d = 3.1.

 

Approx Inst. rate of change = ((I(3.1)-I(2.9))/(3.1-2.9)

 

Can you finish it from here?  You can try an even smaller interval if you want, such as d = 2.99 and 3.01, to get a better approximation.