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Homework Help: Differentiation Question help

  1. May 24, 2010 #1
    1. The problem statement, all variables and given/known data
    The curve C has equation [tex] y=k x^3-x^2+x-5 [/tex] where k is a constant.

    A) Find the derivative of the function with respect to x

    The point A with x-coordinate [tex] -\frac{1}{2} [/tex] lies on C. The tangent to C at A is parallel to the line with equation [tex] 2 y-7 x+1=0 [/tex] .

    Find...

    B) the value of k

    C) the value of the y-coordinate at A.


    2. Relevant equations

    C is [tex] y=k x^3-x^2+x-5 [/tex]
    Equation of the line parallel to the tangent of C at A ( [tex] -\frac{1}{2} [/tex]) [tex] 2 y-7 x+1=0 [/tex] .

    3. The attempt at a solution

    Ok, so I have found the derivative to be equal to: [tex] y'=3 k x^2-2 x+1 [/tex]

    I am having trouble with the find y (and k) because if you were to solve that equation by substituting into it x we then have: [tex] \frac{1}{2} (7 x-1)=y=-2.25 [/tex] but that y value isn't on the tangent line to C. So how would i go about completing these problems?

    Thanks
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. May 24, 2010 #2
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