Question

A pollutant has been leaking steadily into a river. An environmental group undertook a clean-up of the river. The number of units of the pollutant in the river t years after the clean-up began is given by the equation
N(t) = 2t + (1/10t+1)
a) How many units of the pollutant were in the river when the clean-up began?
b) After how many years is the number of units a minimum?
c) What may have happened at this point?

Answer 1

(a) N(0) = ___
(b) find where dN/dt = 0
(c) what do you think?

Answer 2

Thanks for Oobleck's hint.
I use the derivative and set it equal to 0, but the answer is negative. The answer to the textbook is about 11 months.