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Math Help - Complex number

  1. #1
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    Question Complex number

    Given that
    Z1=(13-9i)/(-8+3i) and
    Z2=(-8-7i)/(-11+8i)

    What is z1 + z2 in the form x + yi ?


    I tried and got 18341/23690 +24153i/23690 which is not correct
    ?
    Thanks
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  2. #2
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by taurus View Post
    Given that
    Z1=(13-9i)/(-8+3i) and
    Z2=(-8-7i)/(-11+8i)

    What is z1 + z2 in the form x + yi ?


    I tried and got 18341/23690 +24153i/23690 which is not correct
    ?
    Thanks
    What I would recommend doing is the following: multiple each term by the conjugate of their denominators as follows

    z_1=\frac{13-9i}{-8+3i}\cdot\frac{-8-3i}{-8-3i}=-\frac{131}{73}+\frac{33i}{73}
    z_2=\frac{-8-7i}{-11+8i}\cdot\frac{-11-8i}{-11-8i}=-\frac{32}{185}+\frac{141i}{185}
    (verify)

    Maybe now you can get z_1+z_2 into x+yi form. I get z_1+z_2=-\frac{26571}{13505}+\frac{16398}{13505}i

    Hoped this helped you out!!
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  3. #3
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    that doesnt seem correct either when i enter it in computer
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  4. #4
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by Chris L T521 View Post
    z_2=\frac{-8-7i}{-11+8i}\cdot\frac{-11-8i}{-11-8i}=-\frac{32}{185}+\frac{141i}{185}
    I caught the error right here...it should be \frac{32}{185}+\frac{141i}{185}, not -\frac{32}{185}+\frac{141i}{185}. Thus my answer should turn out to be z_1+z_2=-\frac{21899}{13505}+\frac{16938}{13505}i. This should be the correct answer now. Sorry about that!
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  5. #5
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    hmmmm
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