Cracking The Ap Calculus ab Exam 2018

(Marvins-Underground-K-12) #1
get f′(−8)   =   =   .   This    simplifies  to f′(−8)   =  

= 4.

If  you noticed that    the function    is  simply  the equation    of  a   line,   then    you would   have    seen    that
the derivative is simply the slope of the line, which is 4 everywhere.


  1. −10


We  find    the derivative  of  a   function,   f(x),   using   the definition  of  the derivative, which   is: f′(x)   =

. Here f(x) = 5x^2 and x = −1. This means that f(−1) = 5(−1)^2 = 5 and f


(−1+    h)  =   5(−1+   h)^2    =   5(1 −   2h  +   h^2 )   =   5   −   10h +   5h^2 .  If  we  now plug    these   into    the definition

of   the     derivative,     we  get    f′(−1)   =   =   .   This

simplifies  to  f′(−1)  =    .  Now we  can factor  out the h   from    the numerator   and

cancel  it  with    the h   in  the denominator:    f′(−1)  =       (−10    +   5h).    Now we

take    the limit   to  get f′(−1)  =    (−10   +   5h) =   −10.


  1. 16 x


We  find    the derivative  of  a   function,   f(x),   using   the definition  of  the derivative, which   is: f′(x)   =

. Here f(x) = 8x^2 and f (x + h) = 8(x + h)^2 = 8(x^2 + 2xh + h^2 ) = 8x^2 +16xh


+    8h^2 .  If  we  now     plug    these   into    the     definition  of  the     derivative,     we  get     f′(x)   =  

=    .   This    simplifies  to  f′(x)   =  

. Now we can factor out the h from the numerator and cancel it with the h in the


denominator:    f′(x)   =    (16x   +   8h).    Now we  take    the limit   to  get f′(x)   =   

(16x    +   8h) =   16x.


  1. −20x


We  find    the derivative  of  a   function,   f(x),   using   the definition  of  the derivative, which   is  f′(x)   =   
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