Assignment 7 Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. Using the derivative of f(x) given below, determine the critical points of f(x). 1) f (x) = (x + 4)2 e-x 1) A) -4 B) -2 C) 4 D) -4, -2 SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. For the given function: (a) Find the intervals on which the function is increasing and decreasing. (b) Then identify the function's local extreme values, if any, saying where they are taken on. (c) Which, if any, of the extreme values are absolute? 2) h(x) = x2-5x + 5 2) Provide an appropriate response. 3) Assume that f(x) and g(x) are two functions with the following properties: g(x) and f(x) are 3) everywhere continuous, differentiable, and positive; f(x) is everywhere increasing and g(x) is everywhere decreasing. Which of the following functions are everywhere decreasing? Prove your assertions. i). h(x) = f(x) + g(x) ii). j(x) = f(x) g(x) iii). k(x) = g(x) f(x) iv). p(x) = f(x) g(x) v). r(x) = f(g(x)) = (f g)(x) MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. Using the derivative of f(x) given below, determine the critical points of f(x). 4) f (x) = (x + 2)(x + 10) 4) A) -12 B) 2, 10 C) -10, -2 D) 0, -10, -2 5) f (x) = (x - 1)2(x + 2) 5) A) -2, -1, 1 B) -1, 2 C) -1, 0, 2 D) -2, 1 Using the derivative of f(x) given below, determine the intervals on which f(x) is increasing or decreasing. 6) f (x) = (x - 2) e-x 6) A) Decreasing on (-, 2); increasing on (2, ) B) Increasing on (-, -2); decreasing on (-2, ) C) Increasing on (-, 2); decreasing on (2, ) D) Decreasing on (-, -2); increasing on (-2, ) 1
Provide an appropriate response. 7) Find the absolute maximum and minimum values of f(x) = ln (sin x) on [ 6, 2 3 ]. 7) A) Maximum = 0 at x = 2, minimum = -ln 2 at x = 2 3 B) Maximum = 0 at x = 2, minimum = -ln 2 at x = 6 C) Maximum = 0 at x = 2, minimum = ln 3 2 at x = 2 3 D) Maximum = 0 at x = 0, minimum = -ln 2 at x = 6 SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. For the given function: (a) Find the intervals on which the function is increasing and decreasing. (b) Then identify the function's local extreme values, if any, saying where they are taken on. (c) Which, if any, of the extreme values are absolute? 8) f(x) = xe-x/3 8) 9) f(x) = xex 9) Solve the problem. 10) If f(x) is a differentiable function and f (c) = 0 at an interior point c of f's domain, and if 10) f (x) > 0 for all x in the domain, must f have a local minimum at x = c? Explain. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. For the given expression y (x), sketch the general shape of the graph of y = f(x). [Hint: it may be helpful to find y.] 11) y = x-2/3(x - 2) 11) 2
A) B) C) D) 3
Use the graph of the function f(x) to locate the local extrema and identify the intervals where the function is concave up and concave down. 12) 12) A) Local minimum at x = 3; local maximum at x = -3 ; concave down on (0, ); concave up on (-, 0) B) Local maximum at x = 3; local minimum at x = -3 ; concave up on (0, -3) and (3, ); concave down on (-3, 3) C) Local minimum at x = 3; local maximum at x = -3 ; concave up on (0, -3) and (3, ); concave down on (-3, 3) D) Local minimum at x = 3; local maximum at x = -3 ; concave up on (0, ); concave down on (-, 0) SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. Solve the problem. 13) The accompanying figure shows a portion of the graph of a function that is 13) twice-differentiable at all x except at x = p. At each of the labeled points, classify y and y as positive, negative, or zero. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 4
14) The graphs below show the first and second derivatives of a function y = f(x). Select a possible 14) graph of f that passes through point P. f f A) [NOTE: Graph vertical scales may vary from graph to graph.] B) [NOTE: Graph vertical scales may vary from graph to graph.] 5
C) [NOTE: Graph vertical scales may vary from graph to graph.] D) [NOTE: Graph vertical scales may vary from graph to graph.] SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 15) The graph below shows the position s = f(t) of a body moving back and forth on a 15) coordinate line. (a) When is the body moving away from the origin? Toward the origin? At approximately what times is the (b) velocity equal to zero? (c) Acceleration equal to zero? (d) When is the acceleration positive? Negative? MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. Sketch the graph and show all local extrema and inflection points. 6
16) y = 24x x2 + 9 16) A) Local minimum: (-3,-4) Local maximum: (3,4) Inflection point: (0,0), (-3 3, -6 3),(3 3, 6 3) B) Maximum: (0, 8 3 ) No inflection point 7
C) Local minimum: (-3,- 2) Local maximum: (3,2) Inflection point: (0,0) D) Local minimum: (3,-4) Local maximum: (-3,4) Inflection point: (0,0) Solve the problem. 17) A trough is to be made with an end of the dimensions shown. The length of the trough is to be 17) 25 feet long. Only the angle can be varied. What value of will maximize the trough's volume? A) 55 B) 32 C) 5 D) 30 8
SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question. 18) You are planning to close off a corner of the first quadrant with a line segment 19 units 18) long running from (x,0) to (0,y). Show that the area of the triangle enclosed by the segment is largest when x = y. MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 19) From a thin piece of cardboard 50 in. by 50 in., square corners are cut out so that the sides can be 19) folded up to make a box. What dimensions will yield a box of maximum volume? What is the maximum volume? Round to the nearest tenth, if necessary. A) 33.3 in. by 33.3 in. by 16.7 in.; 18,518.5 in.3 B) 25 in. by 25 in. by 12.5 in.; 7812.5 in.3 C) 33.3 in. by 33.3 in. by 8.3 in.; 9259.3 in.3 D) 16.7 in. by 16.7 in. by 16.7 in.; 4629.6 in.3 20) A small frictionless cart, attached to the wall by a spring, is pulled 10 cm back from its rest position 20) and released at time t = 0 to roll back and forth for 4 sec. Its position at time t is s = 1-10 cos t. What is the cart's maximum speed? When is the cart moving that fast? What is the magnitude of of the acceleration then? A) 10 31.42 cm/sec; t = 0 sec, 1 sec, 2 sec, 3 sec; acceleration is 0 cm/sec2 B) 10 31.42 cm/sec; t = 0.5 sec, 1.5 sec, 2.5 sec, 3.5 sec; acceleration is 0 cm/sec2 C) 3.14 cm/sec; t = 0.5 sec, 1.5 sec, 2.5 sec, 3.5 sec; acceleration is 0 cm/sec2 D) 10 31.42 cm/sec; t = 0.5 sec, 2.5 sec; acceleration is 1 cm/sec2 9
21) The strength S of a rectangular wooden beam is proportional to its width times the square of its 21) depth. Find the dimensions of the strongest beam that can be cut from a 14-in.-diameter cylindrical log. (Round answers to the nearest tenth.) 14" A) w = 9.1; d = 10.4 B) w = 8.1; d = 11.4 C) w = 7.1; d = 12.4 D) w = 9.1; d = 12.4 22) A rectangular field is to be enclosed on four sides with a fence. Fencing costs $7 per foot for two 22) opposite sides, and $3 per foot for the other two sides. Find the dimensions of the field of area 620 ft2 that would be the cheapest to enclose. A) 10.7 ft @ $7 by 58.1 ft @ $3 B) 16.3 ft @ $7 by 38 ft @ $3 C) 58.1 ft @ $7 by 10.7 ft @ $3 D) 38 ft @ $7 by 16.3 ft @ $3 23) Suppose c(x) = x3-24x2 + 30,000x is the cost of manufacturing x items. Find a production level that 23) will minimize the average cost of making x items. A) 11 items B) 13 items C) 14 items D) 12 items Find the most general antiderivative. 24) sin (cot + csc ) d 24) A) csc + cos + C B) sin + C C) cos + C D) sin + + C 25) (5e4x - 3e-x) dx 25) A) 5 4 e 4x - 3e-x + C B) 4 5 e 4x + 3e-x + C C) 5 4 e 4x + 3e-x + C D) 5 4 e 4x + 1 3 e -x + C Solve the problem. 26) f(x) = 3x 2 + 5x + 14 is continuous on [-2, 0] and differentiable on (-2, 0). Then, according to the 26) Mean Value Theorem, there is at least one point c in (-2, 0) at which. A) f(c) = 6 B) f (c) = 6 C) f (c) = -1 D) f(c) = -1 10
Find the most general antiderivative. 1 27) x3 - x 3-1 dx 27) 5 A) C) -1 2x2 - x 4 4 - x 5 + C B) -3x 2-3x3 + C 1 4x4 - x 2 2 + 1 25 + C D) 1 3x4 - x 4 4-1 5x + C Which of the graphs shows the solution of the given initial value problem? 28) dy = 2x, y = -1 when x = 1 28) dx A) B) C) D) 11
Solve the problem. 29) Find the interval or intervals on which the function whose graph is shown is increasing. 29) A) (-, -2] [3, ) B) [-3, 5] C) (-, -3] [5, ) D) [-2, 3] Find the curve y = f(x) in the xy-plane that has the given properties. 30) f(x) has a slope at each point given by - 1 x2 and passes through the point 1 6, 8 30) A) y = 3 x3 + 2 B) y = - 1 x + 10 C) y = 2 x + 2 D) y = 1 x + 2 12