Question 100109: How can I find the vertex while using the quadratic formula?
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! How can I find the vertex while using the quadratic formula?
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The quadratic formula says there are roots at (-b/2a)+sqrt(b^2-4ac)/(2a)
and (-b/2a) - sqrt(b^2-4ac)/2a
So (-b/2a) is the x-value half-way between the two roots.
It is therefore on the axis of symmetry of the parabola.
It is therefore the x-value of the vertex of the parabola
Therefore the vertex is at (-b/2a, f(-b/2a))
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Cheers,
Stan H.
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