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Math Help - help

  1. #1
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    help

    Calculate the amount lzl of the complex number


    would glad if u guys could give me exemple because i cant find what lzl is
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  2. #2
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    Re: help

    Represent z as a+bi; then |z|=\sqrt{a^2+b^2}. See here for multiplication and division on complex numbers.
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  3. #3
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    Re: help

    Quote Originally Posted by Petrus View Post
    Calculate the amount lzl of the complex number


    would glad if u guys could give me exemple because i cant find what lzl is
    Start by simplifying so that it is in z = a + bi form.
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    Re: help

    so a = (9+2i)(7+6i) and b = (7+2i)(-7+7i)?
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  5. #5
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    Re: help

    No, first begin by simplifying the numerator:

    (9+2i)(7+6i)=63+54i+14i+12i^2=51+68i

    Then do the same for the denominator, then factor out any constants and multiply the simplified ratio by the conjugate of the denominator to get the original ratio in the form a + bi.
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  6. #6
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    Re: help

    ok now i got (51+68i)/(-63+35i) so next is to multiplicate with (-63-35i)?
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    Re: help

    "Multiplicate"? Multiply both numerator and denominator by -63- 35i.
    (I didn't check to see if that fraction is actually correct.)
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  8. #8
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    Re: help

    can u check if it is, im not really that good, but i cant see how i can get this to a+bi forme
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  9. #9
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    Re: help

    Yes, that is correct. So you now have:

    \frac{51+68i}{-63+35i}=\frac{1}{7}\cdot\frac{51+68i}{-9+5i}

    We factor out the 7 from the denominator to help keep the computations simple.

    So, multiply the complex fraction by the conjugate of the denominator:

    \frac{1}{7}\cdot\frac{51+68i}{-9+5i}\cdot\frac{-9-5i}{-9-5i}

    This will cause the denominator to be real, and you will then have the complex number in rectangular form.
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  10. #10
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    Re: help

    Quote Originally Posted by Petrus View Post
    Calculate the amount lzl of the complex number
    would glad if u guys could give me exemple because i cant find what lzl is
    Make it easy. Just calculate \frac{|9+2i||7+6i|}{|7+2i||-7+7i|}~.
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  11. #11
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    Re: help

    Quote Originally Posted by Plato View Post
    Make it easy. Just calculate \frac{|9+2i||7+6i|}{|7+2i||-7+7i|}~.
    But is it easier to evaluate four moduli then multiply/divide them, or to simplify to a single complex number and taking the modulus?
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