Math 181 - Practice Exam 2

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Math 181 - Practice Exam 2

Problem 1 A population of dinosaurs produces offspring which numbers

P ( t ) = − 0 .

3 t 2 + 0 .

1 t + 10 for times t in the interval [ − 4 , 0]. At the same time, dinosaurs die from various causes, deaths numbering D ( t ) = 0 .

2 t

2

+ 0 .

1 t in the same timespan.

a)The net increase of the population is offspring - death numbers. Find the rate of change of this net increase at t = − 4.

b) Find the equation of the tangent line of P ( t ) at t = − 4 and sketch it, together with the graph of P , over the interval [ − 4 , 0]. Your graph should include the values of P at − 4 , − 2 , 0.

Problem 2 Consider the function

2 t − 3 f ( t ) = t 2 + 2 t − 4 a) Find the derivative of f using quick rules.

b) Find all relative maxima and minima of f .

c) Tell where the function f is increasing and where it is decreasing.

d) Find the maximum and minimum value of f on the interval [ − 3 , 0].

e) Find the equation of the tangent line to the graph of f at t = 2.

Problem 3 A farmer wants to fence in a rectangular field using strong fence on two opposite sides, costing $ 5 per foot, and cheap fence on the two other sides, costing $ 4 per foot.

a) What is the minimum cost to fence in 4000 square feet in this manner?

b) What if the farmer can use an existing 60-foot wall instead of strong fence?

Problem 4 Find the following derivatives, using Quick Rules. No need to simplify.

y =

3 x

2 − x + 3 y = x 2 − 4 y = ( x

2 − 1)

2

4 x + 2 y = ( x

3

+ 2 x − 1)

100

Problem 5 A cylindrical barrel is to be built from sheet metal. Assume that the surface area of the barrel is

A = 2 πr

2

+ 2 πhr if h is its height and r the radius of the base. The volume is V = πr

2 h . If you want to build a barrel with a volume of 432 π cubic feet, what are the dimensions that use the least amount of material?

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