Hellppppp!!!! Write the equation of a quadratic function that contains the points (1,21), (2,18), and (-1,9).

Question

Hellppppp!!!!

Write the equation of a quadratic function that contains the points (1,21), (2,18), and (-1,9).

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Dulcie 7 months 2021-08-02T06:16:34+00:00 1 Answers 3 views 0

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    2021-08-02T06:18:28+00:00

    Answer:

    y=-3x^{2} +6x+18

    Step-by-step explanation:

    y=ax^{2} +bx+c

    Substitute the three points we have.

    21=a+b+c\\18=4a+2b+c\\9=a-b+c\\

    Take the first less the third.

    2b=12\\b=6

    15=a+c\\6=4a+c\\15=a+c\\

    Take the second and subtract the first.

    -9=3a\\a=-3

    Therefore, we can calculate c.

    c=18.

    Therefore, our equation is y=-3x^{2} +6x+18

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