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Sullivan  04 apcalc4e 45342 ch02 166 233 5pp  August 7, 2023  12:54



               202     Chapter 2 • The Derivative and Its Properties

               85. The line x = c, where c > 0, intersects the           (a) If the tangent line to the cubic at the point P is parallel to the
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                   cubic y = 2x + 3x − 9 at the point P and intersects the  line tangent to the parabola at the point Q, find the number c.
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                   parabola y = 4x + 4x + 5 at the point Q, as shown in the
                   figure below.                                         (b) Write an equation for each of the two tangent lines described
                                      y  x  c                              in (a).
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                                                                      86. f (x) = Ax + B, A > 0.
                                                                         (a) Find c, c > 0, in terms of A so that the tangent lines to the
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                                               y  2x  ! 3x   9             graph of f at (c, f (c)) and (−c, f (−c)) are perpendicular.
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                           y  4x  ! 4x ! 5                              (b) Find the slopes of the tangent lines in (a).
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                                                                         (c) Find the coordinates, in terms of A and B, of the point of
                                                                            intersection of the tangent lines in (a).
                                2             2     4  x
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                                                                                         Preparing for the AP Exam
                   R
               AP Practice Problems
               Multiple-Choice Questions
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             194  1. If g(x) = x, then g (7) =                   199  9. Find f (1) if f (x) = 3e − 5x + 2 ln x − 5.
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                   (A) 0   (B) 1   (C) 7  (D)                           (A) −15   (B) 3e − 5  (C) 3e − 18  (D) 3e − 13
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                                                                                  4
                                                                           3(2 + h) − 3 · 16
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             197  2. The line x + y = k, where k is a constant, is a line tangent  195 10. lim  =
                                              2
                   to the graph of the function f (x) = x − 5x + 2.     h→0      h
                   What is the value of k?                              (A) 0   (B) 32  (C) 48   (D) 96
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                   (A) −1   (B) 2   (C) −2   (D) −4              197 11. Which is an equation of the line tangent to the graph
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                                                                                      2
                                                                        of f (x) = x + 3x + 2 at the point where f (x) = 2?
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             197  3. An object moves along the x-axis so that its position
                                  2
                   at time t is x(t) = 3t − 9t + 7. For what time t is  (A) y = 2x + 2    (B) y = 2x + 2.929
                   the velocity of the object zero?
                                                                        (C) y = 2x + 1.678  (D) y = 2x − 2.929
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                   (A) −3   (B) 3   (C)     (D) 7
                                        2                         Free-Response Questions
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             198  4. If f (x) = e , then ln( f (3)) =            197 12. For the function f (x) = x + 4
                                                                        (a) Find f (1).
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                   (A) 3   (B) 0   (C) e  3  (D) ln 3
                                                                        (b) Find an equation of the line tangent to the graph
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             197  5. An equation of the line tangent to the graph          of f at x = 1.
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                            3
                   of g(x) = x + 2x − 2x + 1 at the point where x = −2 is  (c) Find f (−4).
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                   (A) x + 2y = 12  (B) y + 2x = 9                      (d) Find an equation of the line tangent to the graph
                                                                           of f at x = −4.
                   (C) 2x + y = −9  (D) y − 2x = 9
                                                                        (e) Find the point of intersection of the two tangent lines
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             195  6. The line 9x − 16y = 0 is tangent to the graph         found in (b) and (d).
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                   of f (x) = 3x + k, where k is a constant, at a point in
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                   the first quadrant. Find k.                                 −x + x + 1 if  x < 0
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                                                                 197 13. f (x) =   1      if  x = 0
                       3        3         3        9                                x
                   (A)      (B)      (C)      (D)                                  e      if  x > 0
                       32       16       64       64
                                                                        (a) Determine whether f is continuous at x = 0. Justify your
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             199  7. If f (x) = 3x + ln x, find f (1).                     answer.
                   (A) 2   (B) 0   (C) 3  (D) 4                         (b) Find an equation of the line tangent to the graph of f
                                                                           at x = − 1.
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             197  8. The cost C (in dollars) of manufacturing x units of a product  (c) Find an equation of the line tangent to the graph of f
                              2
                   is C(x) = 0.3x + 4.02x + 3500.
                                                                           at x = 1.
                   What is the rate of change of C when x = 1000 units?
                   (A) 307.52  (B) 0.60402  (C) 604.02  (D) 1020
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