Relative Or Local Extrema Highest Or Lowest Point in the Neighborhood

Student Study Session

Optimization

Relative or Local Extrema – highest or lowest point in the neighborhood

First derivative test

Candidates – critical numbers (x-values that make zero or undefined where
is defined)
Test –(1) set up an number line; label with candidates

(2) test each section to see if is positive or negative

(3) relative maximum occurs when changes from + to –
relative minimum occurs when changes from – to +

Second derivative test

Candidates – critical numbers (x-values that make zero or undefinedwhere
is defined)
Test –(1) substitute each critical number into the second derivative

(2), relative minimum

, relative maximum

(3), the test fails

Absolute or Global Extrema – highest or lowest point in the domain

Absolute Extrema Test
Candidates – critical numbers and endpoints of the domain
Test –(1) find the y-values for each candidate

(2)the absolute maximum value is the largest y-value,
the absolute minimum value is the smallest y-value

Students need to be able to:

Locate a function’s relative (local) and absolute (global) extrema using the first derivative test, second derivative test or closed interval test (also known as candidates test).
Reason from a graph without finding an explicit rule that represents the graph.
Write justifications and explanations.
Must be written in sentence form.
Avoid using the pronoun “it” when justifying extrema.
Use "the function,""the derivative," or "the second derivative" instead of "the graph" or "the slope" in explanations.

Optimization

Student Study Session

Multiple Choice

1.(calculator not allowed) (1985 AB16)

The function defined by for all real numbers has a relative maximum at

(A)

(B)

(C)

(D)

(E)

2.(calculator not allowed) (1973 BC27 appropriate for AB)

If and the domain is the set of all x such that , then the absolute maximum value of the function occurs when x is

(A)

(B)

(C)

(D)

(E)

3.(calculator not allowed) (1988 AB45)

The volume of a cylindrical tin can with a top and a bottom is to be cubic inches. If a minimum amount of tin is to be used to construct the can, what must be the height, in inches, of the can?

(A)

(B)

(C)

(D)

(E)8

4.(calculator not allowed) (1993 AB15)

For what value of x does the function have a relative maximum?

(A)

(B)

(C)

(D)

(E)

5.(calculator not allowed) (1993 AB44)

What is the minimum value of ?

(A)

(B)

(C)

(D)

(E) has no minimum value.

6.(calculator not allowed) (1993 BC14appropriate for AB)

The derivative of is . At how many points will the graph of have a relative maximum?

(A)None

(B)One

(C)Two

(D)Three

(E)Four

7.(calculator not allowed) (1993 BC36appropriate for AB)

Consider all right circular cylinders for which the sum of the height and the circumference is 30 centimeters. What is the radius of the one with maximum volume?

(A)cm

(B) cm

(D)

(E)

8.(calculator not allowed) (1969 AB11/BC11)

The point on the curve that is nearest the point occurs where y is

(A)

(B)

(C)

(D)

(E)none

9.(calculator not allowed) (1997 BC9appropriate for AB)

The function is defined on the closed interval . The graph of its derivative is shown above. At what value of x is does the absolute minimum of occur?

(A)0

(B)2

(D)6

(E)8

10. (calculator not allowed) (1988 BC45)

What is the area of the largest rectangle that can be inscribed in the ellipse ?

(A)

(B)12

(D)

(E)36

11.(calculator allowed) (1997 AB82)

If , what is the minimum value of the product of xy?

(A)

(B)

(C)

(D)

(E)

Free Response Questions

12.(calculator not allowed) (2008 AB6b)

Let f be the function given byfor all . The derivative of is given by.

(b)Find the x-coordinate of the critical point of . Determine whether this point is a relative minimum, a relative maximum, or neither for the function. Justify your answer.

13. (calculator allowed) (2009 AB2b)

The rate at which people enter an auditorium for a rock concert is modeled by the function R given by for hours; is measured in people per hour. No one is in the auditorium at time , when the doors open. The doors close and the concert begins at time .

(b)Find the time when the rate at which people enter the auditorium is a maximum. Justify your answer.

14.(calculator allowed) (2010 AB2d)

(d)At 8 P.M., volunteers began to process the entries. They processed the entries at a rate modeled by the function P, where hundreds of entries per hour for. According to the model, at what time were the entries being processed most quickly? Justify your answer.

15.(calculator not allowed) (2010 AB5c)

The function is defined and differentiable on the closed interval and satisfies. The graph of, the derivative of, consists of a semicircle and three line segments, as shown in the figure above.

(c)The function is defined by. Find the x-coordinate of each critical point of , where, and classify each critical point as the location of a relative minimum, relative maximum, or neither a minimum nor a maximum. Explain your reasoning.

16.(calculator not allowed) (2009 AB6c)

The derivative of a function f is defined by.

The graph of the continuous function, shown in the figure above, has x-intercepts at and . The graph onis a semicircle, and.

(c)For , find the value of x at which has an absolute maximum. Justify your answer.

17.(calculator allowed) 2007 AB2/BC2

The amount of water in a storage tank, in gallons, is modeled by a continuous function on the time interval where t is measured in hours. In this model, rates are given as follows:

(i)The rate at which water enters the tank is gallons per hour for

(ii)The rate at which water leaves the tank is

gallons per hour.

The graphs of f and g, which intersect at and are shown in the figure above.

At time, the amount of water in the tank is 5000 gallons.

(c)For , at what time t is the amount of water in the tank greatest? To the nearest gallon, compute the amount of water at this time. Justify your answer.