Ariel G.

asked • 02/20/21

How do you find the vertex of -9x^2+156x+480

please explain how I find the vertex of this!

Brenda D.

tutor
You can look up the standard form of a parabola and the relationships between the coefficients and features of of the curve in your text or on the internet. Once you determine the x coordinate you can plug that back in to your standard from expression above to find the y coordinate. You can also graph your parabola to confirm the coordinates you calculate based on the given coefficients. You can graph your parabola at Desmos.com
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02/20/21

1 Expert Answer

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Davide M. answered • 02/20/21

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PhD in Mathematics, former UCLA Researcher: Math and Physics Tutor
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Given a parabola of the form y=ax2+bx+c the x-coordinate of the vertex is -b/2a and the y-coordinate of the vertex is c -b2/4a

In this exercise we have a=-9, b=156, c=480

If you plug in the numbers you have that the x-coordinate is 26/3 and the y-coordinate is 1156


Best,

Davide

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Ariel G.

thank you so much does the equation looks like this afterwards: -9(x+26/3)^2+1156?
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02/20/21

Davide M.

tutor
In this case there is no equation afterwards, you simply have a pair (X_v,Y_v) where X_v is the x coordinate of the vertex, and Y_v is the y coordinate of the vertex. In this particular case you have X_v=26/3 and Y_v=1156. The only equation here is the equation of the parabola y=-9x^2+156x+480 If something is not clear let me know. Best, Davide
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02/20/21

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