Cracking The Ap Calculus ab Exam 2018

(Marvins-Underground-K-12) #1
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  1. B The formula for the area under a curve using right-endpoint rectangles is: A = (y 1 + y 2


+   y 3     +...+   yn),    where   a   and b   are the x-values    that    bound   the area    and n   is  the number  of

rectangles. Since   we  are interested  in  the right-endpoints,    the x-coordinates   are x 1     =    ,  x 2     =    ,

x 3     =    ,  and x 4     =   2.  The y-coordinates   are found   by  plugging    these   values  into    the equation    for

y,  so  y 1     =   3.5625, y 2     =   4.25,   y 3     =   5.0625, and y 4     =   6.  Then,   A   =       (3.5625 +   4.25    +

5.0625 + 6) = 4.71875.


  1. C The formula for the area under a curve using inscribed trapezoids is: A = (y 0 +


2 y 1   +   2yn−1   +   yn, where   a   and b   are the x-values    that    bound   the area    and n   is  the number  of

rectangles. The x-coordinates   are x 0     =   1,  x 1     =    ,  x 2     =    ,x 3   =    ,  and x 4     =   2.  The y-coordinates

are found   by  plugging    these   values  into    the equation    for y,  so  y 0     =   3,  y 1     =   3.5625  y 2     =   4.25    y 3     =

5.0625, and y 4     =   6.  Then,   A   =    (3 +   2(3.5625)   +   2(4.25) +   2(5.0625)   +   6)  =

4.34375.


  1. D Use the Fundamental Theorem of Calculus: f (x) dx = F (b) − F (a) and u-substitution. For


this    problem,    u   =   x^2     and du  =   2x  dx. Then:

dx  =    du =       =       −       =   0


  1. D The volume of a sphere is V = π R 3 . Using differentials, the change will be dV = 4πR^2 dR.


Substitute  in  R   =   10  and dR  =   0.02    to  get

dV  =   4π(10^2 )(0.02)

dV  =   8π  ≈   25.133  cm^3
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