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Math Help - Complex no.s raised to exponents & divided...

  1. #1
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    Complex no.s raised to exponents & divided...

    Hi guys,

    i have a problem...it goes like this:

    Given: z1= 2,5+8i and z2= 0,5-3i

    2) Now Calculate: (z1)^2/(z2)^3

    This is what my answer looks like: -947,969/874,704 - 1309,438i/874,704

    I need to know where i went wrong please?

    Thanks in advance...
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  2. #2
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    Re: Complex no.s raised to exponents & divided...

    Quote Originally Posted by Toyboy View Post
    Given: z1= 2,5+8i and z2= 0,5-3i

    Now Calculate: (z1)^2/(z2)^3

    This is what my answer looks like: -947,969/874,704 - 1309,438i/874,704

    I need to know where i went wrong please?
    Well, (5/2 + 8i)^2 = (160i - 231) / 4
    and (1/2 - 3i)^3 = (198i - 107) / 8
    SO:
    [(160i - 231) / 4] / [(198i - 107) / 8] = (320i - 462) / (198i - 107)

    Hope that helps...
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  3. #3
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    Re: Complex no.s raised to exponents & divided...

    But since you don't tell us what you did there is no way to say what, if anything, you did wrong!
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    Re: Complex no.s raised to exponents & divided...

    Quote Originally Posted by HallsofIvy View Post
    But since you don't tell us what you did there is no way to say what, if anything, you did wrong!
    My apologies, this is what i did:

    (2,5+8i)^2/(0,5-3i)^3
    (2,5+8i)(2,5+8i)/(0,5-3i)(0,5-3i)(0,5-3i)

    ....mulitplied it all out and ended up with this: -947,969/874,704 - 1309,438i/874,704
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    Re: Complex no.s raised to exponents & divided...

    Quote Originally Posted by Toyboy View Post
    (2,5+8i)(2,5+8i)
    Do you get what I got when you complete that one...see my previous post... ??
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  6. #6
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    Re: Complex no.s raised to exponents & divided...

    Quote Originally Posted by Wilmer View Post
    Do you get what I got when you complete that one...see my previous post... ??
    Sorry i missed your post...

    Nope, it does not, mine equates to -1.084-1.497i
    Your answer equates to 4.318+1.61(recurrring 61)
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  7. #7
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    Re: Complex no.s raised to exponents & divided...

    Sorry, but got no idea what you're talking about or doing...
    mine equates to -57.75 + 40i ; or to -17.75 if 1 is used instead of i

    I'll ask you once more:
    I get: (2.5 + 8i)^2 = (160i - 231) / 4
    What do you get: (2.5 + 8i)^2 = ?
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  8. #8
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    Lightbulb Re: Complex no.s raised to exponents & divided...

    Quote Originally Posted by Toyboy View Post
    Given: z1= 2,5+8i and z2= 0,5-3i
    2) Now Calculate: (z1)^2/(z2)^3
    This is what my answer looks like: -947,969/874,704 - 1309,438i/874,704
    \frac{{z1}^2}{{z2}^3}=2.22 +1.13 i
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  9. #9
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    Re: Complex no.s raised to exponents & divided...

    Quote Originally Posted by MaxJasper View Post
    \frac{{z1}^2}{{z2}^3}=2.22 +1.13 i
    Agree. (320i - 462) / (198i - 107) = ~2.226798 + ~1.129962 i
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