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A certain parabola passes through the points (5,1) and (13,-7) and has the y-axis as its directrix.what are the coordinates of all points at which the vertex of this parabola could be located ?

- sri340
**Posts:**1**Joined:**Wed Nov 16, 2011 1:08 pm

sri340 wrote:A certain parabola passes through the points (5,1) and (13,-7) and has the y-axis as its directrix.what are the coordinates of all points at which the vertex of this parabola could be located ?

The generic formula for this particular conic is 4p(x - h) = (y - k)

Since the y-axis is the directrix, then the vertex and focal point are directly to the right, given the locations of the two listed points. By definition, then, the vertex must be at the point (h, k) = (p, k). Use this information, along with the two given points, to create a system of two equations in two unknowns.

- nona.m.nona
**Posts:**257**Joined:**Sun Dec 14, 2008 11:07 pm

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