SOLUTION: The vertex of this parabola is at (4, -3). When the x-value is 5, the y-value is -6. What is the coefficient of the squared expression in the parabola's equation?

Question 297765: The vertex of this parabola is at (4, -3). When the x-value is 5, the
y-value is -6. What is the coefficient of the squared expression in the parabola's equation?

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
The vertex of this parabola is at (4, -3). When the x-value is 5, the
y-value is -6. What is the coefficient of the squared expression in the parabola's equation?
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y = ax^2 + bx + c
Find a,b,c
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From the vertex info: 4 = -b/(2a)
b = -8a
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So y = ax^2 (-8a)x + c
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From the (5,-6) and the (4,-3) info:
-6 = a(25) -8a(5) +c
-3 = a(16) -8a(4) +c
----------------------------
Rearrange the two equations and solve for a and for c.
Since b = -8a you also will know b.
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Now you know a,b, and c so you can write the
equation of the parabola.
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Cheers,
Stan H.
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