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anonymous

  • one year ago

Write the equation of the quadratic function with roots -2 and 4 and a vertex at (1, 9).

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  1. welshfella
    • one year ago
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    the vertex form of a quadratic is a(x - h)^2 + k where the vertex is at (h,k)

  2. welshfella
    • one year ago
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    so in your case we have f(x) = a(x - 1)^2 + 9

  3. welshfella
    • one year ago
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    now you need to find the value of a which you can do using the given roots

  4. anonymous
    • one year ago
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    so what is a?

  5. welshfella
    • one year ago
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    a is a number to be found

  6. welshfella
    • one year ago
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    the roots are -2 and 4 so points of intersection on x-axis are (-2,0) and (4,0) So plugging these values into the above equation and solving for a will give you the final equation

  7. anonymous
    • one year ago
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    I'm really not good at this. but i think i'm kinda getting it? could you just show me please?

  8. welshfella
    • one year ago
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    ok f(x) = 0 when a - -2 so 0 = a(-2-1)^2 + 9 0 = 9a + 9 -9a = 9 a = -1 so we;ve found a

  9. anonymous
    • one year ago
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    so the answer is f(x) = -1(x - 1)^2 + 9?

  10. welshfella
    • one year ago
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    yes

  11. anonymous
    • one year ago
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    thanks so much. i will fan and medal you. :)

  12. welshfella
    • one year ago
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    they might want it in standard form though just expand and simplify

  13. welshfella
    • one year ago
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    yw ty

  14. welshfella
    • one year ago
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    they haven't asked for that so leaving in in the above form should be ok

  15. anonymous
    • one year ago
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    yep, that should be fine. thanks again.

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