From: Doug Shields
To: Teacher2Teacher Public Discussion
Subject: Algebraic expression of the vertex of the Phantom Parabola
I love the phantom parabola idea. Here might be an addendum to that day's lecture: The vertex of the parabola corresponding to y = ax^2 + bx + c is at (-b/2a, -b^2/4a + c). If the roots of the equation are complex, and we write the solutions as r +/- si, then the coordinates of the vertex are simply (r, as^2). Doug.
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