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Finding points on a tangent line

  1. Nov 5, 2011 #1
    1. The problem statement, all variables and given/known data

    Find the point(s) on the graph of the function at which the tangent line has the indicated slope. (If an answer does not exist, enter DNE.)

    g(x) = (1/3)x^3 - (1/2)x^2 - 4x +8

    mtan=-4

    2. Relevant equations



    3. The attempt at a solution

    firstly i derived g(x) to give x^2-x-4
    as tangent line = -4 substituted into equation to give x^2-x-4=-4
    manipulated to get x^2-x=0
    that gave me x=0 or x=-1
    used those values in original function to find y values
    points i obtained were (0,8) and (-1,67/6)

    when i enter these with lowest x value first it says i am wrong please help
     
  2. jcsd
  3. Nov 5, 2011 #2
    Since this is just a silly brainfart mistake I'm going to give you the answer, x=-1 is not a solution, you made a silly mistake when you solved the quadratic.
     
  4. Nov 5, 2011 #3
    ahhh i cant believe i missed that

    thanks
     
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