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Math Help - Quadratic formula to find zero

  1. #1
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    Exclamation Quadratic formula to find zero

    Use the quadratic formula to find the zeros of the function

    f(x)=x^2-6x+18

    i get

    x=6 +- Square r0ot of -6^2-4(1)(18)

    x=6 +- squareroot of 36-72

    which = -36

    then
    6 +_ 6i
    __________

    2(1)

    =

    3+- 3i

    right...


    Now iT states to put it in factored form

    f(x)= a(x-r1)(x-r2)

    where a= ?

    r1= ?

    r2=?

    i tried putting a=3

    r1=3i
    r2=3i

    but i guess im wr0ng help please...

    =[

    thank you so much to everyone on the forum!
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by Jackie10 View Post
    Use the quadratic formula to find the zeros of the function

    f(x)=x^2-6x+18

    i get

    x=6 +- Square r0ot of -6^2-4(1)(18)

    x=6 +- squareroot of 36-72

    which = -36

    then
    6 +_ 6i
    __________

    2(1)

    =

    3+- 3i

    right...


    Now iT states to put it in factored form

    f(x)= a(x-r1)(x-r2)
    Hi Jackie10,

    I would do it this way:

    Since the roots are 3+3i and 3-3i, the factored form would be:

    f(x) = [x-(3+3i)][x-(3-3i)] = (x-3-3i)(x-3+3i)
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  3. #3
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    =] Thank you so then the top part is correct right...

    and what do i put for a in the formula?
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  4. #4
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    Quote Originally Posted by Jackie10 View Post
    =] Thank you so then the top part is correct right...

    and what do i put for a in the formula?
    "a" is the coefficient of x^2, so a=1

    r1 doesn't equal -3i
    r1=3-3i
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