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Homework Help: Quadratic and linear Intersection

  1. Jan 24, 2016 #1
    1. The problem statement, all variables and given/known data
    How many points of intersection does the line y = x have with the parabola y = 6x − x2 −10 ?
    A) none
    B) one
    C) two
    D) three
    E) more than three

    2. Relevant equations

    3. The attempt at a solution
    x = 6x - x^2 - 10
    -x^2+5x - 10
    Used b^2 - 4ac to check the number of intersections.

    The answer I got is . However my teacher marked it as incorrect. I still cannot find the problem, please help. If my teacher marked it wrong, please tell me so because I think he did. Thanks.
  2. jcsd
  3. Jan 24, 2016 #2
    Graphing makes it clear.
  4. Jan 24, 2016 #3
    What was your answer? What did you plug in for b2 - 4ac? Your approach is correct, but I'd draw a graph to be sure. (Hint: you know the parabola is negative, and you know the y-intercept is -10.)
  5. Jan 24, 2016 #4


    Staff: Mentor

    Where did the = go? You have it two lines above, but not in the line above here.
    Is what?
    Your teacher marked what as incorrect?
    You need to give us enough information so that we can provide meaningful help.
  6. Jan 24, 2016 #5
    Sorry I know the right answer now. However I typed it in wrong. I forgot to write that the answer i got is A . Thanks
  7. Jan 25, 2016 #6


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Are you saying that your teacher's answer is not A, or that you typed the question wrongly (or both)?
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