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Solving for k

  1. Mar 3, 2015 #1
    1. The problem statement, all variables and given/known data
    If the slope of the curve y=−2kx^3+4kx at x=3 is 25, what is the value of k?

    2. Relevant equations
    f(x)=xn
    f'(x)=nxn-1

    3. The attempt at a solution
    y=f(x)

    f(x)=-2kx3+4kx
    f'(x)=-6kx2+4k
    x=3
    f'(3)=-50k

    -50k = 25
    -k=1/2
    k=-1/2

    Did I do it right?
     
  2. jcsd
  3. Mar 3, 2015 #2

    Dick

    User Avatar
    Science Advisor
    Homework Helper

    Yes.
     
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