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Homework Help: I'v quistion on Quadratic Functions

  1. Mar 12, 2010 #1
    1. The problem statement, all variables and given/known data
    Let f(x)= 125x-6x2 find the maximum value of f to four decimal places graphically


    2. Relevant equations
    (x)= 125x-6x2


    3. The attempt at a solution
    1. The problem statement, all variables and given/known data

    attempt solution:

    x=-b+[tex]\sqrt{}b2-4ac[/tex]/2a

    x=-125+[tex]\sqrt{}1252-4(-6)(0)[/tex]/2a

    x= 0/-12=0

    x=-b-[tex]\sqrt{}b2-4ac[/tex]/2a

    x=-b-[tex]\sqrt{}b2-4ac[/tex]/2a

    x=(-125-125)/-12

    x=-125/6


    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
    Last edited: Mar 12, 2010
  2. jcsd
  3. Mar 12, 2010 #2
    Do you know how to make graph for quadratic equations?
     
  4. Mar 12, 2010 #3
    and also show your attempt otherwise nobody will help you here because of the rules of PF
     
  5. Mar 12, 2010 #4
    ya I know to make graph for quadratic
     
  6. Mar 12, 2010 #5

    Mentallic

    User Avatar
    Homework Helper

    Ok then, do you realize there is a symmetry of any parabola on either end of its max/min? So if you find the roots of the quadratic, what can you deduce about the coordinates of the max/min from that?
     
  7. Mar 12, 2010 #6

    Mark44

    Staff: Mentor

    What you've done is attempt to find the x-intercepts, which is not at all what this problem is asking for. In addition, there is one intercept that you did not find, and the one you found is incorrect.
     
  8. Mar 12, 2010 #7
    Think what 'maximum' is. Note that maximum does not refer to an x value.

    There is a formula to determine the maximum or minimum value of a parabola. Give it a hard think. It'll come to you.
     
  9. Mar 12, 2010 #8

    Mark44

    Staff: Mentor

    The OP is not supposed to use a formula. He/she is supposed to find the maximum by looking at a graph of the function.
     
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