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Finding equations w/ two given points:

  1. Oct 12, 2006 #1
    Ok there are two give points and I need to find the equation:

    Points: (-3,0), (-.5,0)

    My work:


    Completed the square:

    -15= x^2+3.5x
    y= (x+1.75)^2+11.9375

    What did I do wrong??
  2. jcsd
  3. Oct 12, 2006 #2
    [tex] y = (x+3)(x+.5) = x^{2}+3.5x + 1.5[/tex]

    you multiplied 3 by 5, instead of 3 by 0.5
  4. Oct 12, 2006 #3
    ohhh lol thanks.
  5. Oct 12, 2006 #4


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    Science Advisor

    Why did you assume a quadratic function? Two points determine a straight line. The constant function y= 0 passes through (-3, 0), (-5, 0).
    In fact there are an infinite number of functions whose graph pass through those two points.
  6. Oct 12, 2006 #5
    Halls, he meant the zeros of the function. He is doing quadratic equations after all.
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