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Math Help - Imaginary part of number

  1. #1
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    Imaginary part of number

    Find the real and imaginary parts of the complex number.
    4 - -11


    I know that the real part of this is 4, but I don't know the imaginary portion.
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  2. #2
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    a + bi

    a is the real part

    bi is the imaginary

    4 - \sqrt{-11} = 4 - i\sqrt{11}
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  3. #3
    Senior Member mollymcf2009's Avatar
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    You can't take the square root of a negative number, so:

    4 - \sqrt{-11} = 4 - (\sqrt{11})(\sqrt{-1})

    \sqrt{-1} = i

    So,

    4 - i\sqrt{11}
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  4. #4
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    Quote Originally Posted by skeeter View Post
    a + bi

    a is the real part

    bi is the imaginary

    4 - \sqrt{-11} = 4 - i\sqrt{11}
    Just to clarify for the OP:

    The imaginary part is b. The i does not get included. The imaginary part is the coefficient of i.
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  5. #5
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    Quote Originally Posted by mollymcf2009 View Post
    You can't take the square root of a negative number, so: Mr F says: Yes you can. And in what follows you do!

    4 - \sqrt{-11} = 4 - (\sqrt{11})(\sqrt{-1})

    \sqrt{-1} = i

    So,

    4 - i\sqrt{11}
    ..
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  6. #6
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    Quote Originally Posted by mr fantastic View Post
    Quote:
    Originally Posted by mollymcf2009
    You can't take the square root of a negative number, so: Mr F says: Yes you can. And in what follows you do!





    So,


    ..
    haha well technically " you cant take the square root of a negative number IN REAL NUMBERS. " we can take it and do in the complex number system
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  7. #7
    Senior Member mollymcf2009's Avatar
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    Wow, I'll bet OP is REALLY confused now!

    You can't take the square root of a REAL number. Thank you potato salad!

    From Mr. Fantastic's post:
    The imaginary part is
    b. The i does not get included. The imaginary part is the coefficient of i.

    The definition of an imaginary number is a number when squared gives a negative result. i^2 = -1

    "i" is a symbol with the property that i^2 = -1

    The "real" part of the complex number 4-i\sqrt{11} = the real number "4" AND the imaginary part of the complex number is the real number \sqrt{11}

    How's that sound?
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  8. #8
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    Quote Originally Posted by mollymcf2009 View Post
    Wow, I'll bet OP is REALLY confused now!

    You can't take the square root of a REAL number. Thank you potato salad!

    How's that sound?
    maybe stick the word "negative" in there somewhere?
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  9. #9
    Senior Member mollymcf2009's Avatar
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    LOL! After all that! Yes, real NEGATIVE number! Keepin' me straight!
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