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Finding vertex of parabola

  1. May 27, 2010 #1
    1. The problem statement, all variables and given/known data Sorry for such an elementary question, but I'm struggling thru Int Alg. Today's nightmare involves a downward parabola. An arch supporting a bridge has the equation y=-0.0022x^2 + 1.578x + 0. Position of left side parabolic arch is (0,0). Using x = -b/2a, I calculated the symmetrical point of the parabola at (358.6363,0). If this is correct, the vertex x-coordinate is 179.31815. I'm stuck at finding the y coordinate of the vertex. Any help would be greatly appreciated.

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. May 27, 2010 #2


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    You know that y=-0.0022x^2 + 1.578x. What is y when x = 179.31815?
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