M106 Practice Exam 3
[Note: These problems appeared on
my M106 exams in the fall of 1995.]
Instructions: Show all of your work and clearly
explain your answers.
This is particularly important on problems
with a numerical answer, to allow the possibility
of partial credit. No books are allowed
during the exam, but you may use your calculator.
Problem [1] Suppose that f(x) is a differentiable function
such that f(2)=3, f'(2)=5 and f'(3)=7.
- (a) Find dy/dx when x = 2 and y = -1, given that yf(x) + xy3 = -5.
- (b) Find the line tangent to the graph of
y = x7 - 8x2 + 35x - 40 at x = 0.
Problem [2] Suppose the graph below
gives the derivative g(x) of some function y = G(x).
- (a) Circle each x-value on the x-axis in the graph
for which the original function G(x) has a critical point.
- (b) Put an X (for maX) in each of your critical point
circles for which the critical point is a
local maximum of the original function G(x).
- (c) Put an N (for miN) in each of your critical point
circles for which the critical point is a
local minimum of the original function G(x).
- (d) Put an i at each point of the graph for which the original
function G(x) has a point of inflection.
Problem [3] Consider the
limit as h approaches 0 of [ln(e+h)-1]/h.
- (a) This limit is actually the definition of the derivative of some function
f(x) at some value x = a. Determine f(x) and a.
- (b) Use your answer to (a) to determine the limit exactly.
- (c) Use L'Hopital's rule to determine the limit exactly a second way.
Problem [4] Let h(x) = x2x.
- (a) For what exact x-value is h(x) as small as possible?
Show how you find the correct x-value and how you know
h(x) has a minimum there.
- (b) For what exact x-value or values in the range -2 <= x <= -1
is h(x) as large as possible? Show how you find the
correct x-value and how you know for values in the given range that
h(x) has a maximum there.
Problem [5] Farmer Brown wants to fence off three sides of
a rectangular area; the fourth side runs along a river and does not need a fence.
She wants there to be 5000 square yards of land in the rectangle.
What are the dimensions of the rectangle needing the least amount of fencing?