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Math Help - Multiplication of complex numbers

  1. #1
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    Smile Multiplication of complex numbers

    If z = 3 + 4i and w = 1 - 2i, calculate:

    (z - w)

    Please show any working out. Thanks.
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  2. #2
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    Quote Originally Posted by Joker37 View Post
    If z = 3 + 4i and w = 1 - 2i, calculate:

    (z - w)

    Please show any working out. Thanks.
    z - w = (3 + 4i) - (1 - 2i) = 2 + 6i<br />

    now calculate (2 + 6i)^2
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  3. #3
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    Hello, Joker37!

    This is straight-forward algebra.
    Exactly where is your difficulty?


    \text{If }\,z \,=\, 3 + 4i\text{ and }w \,=\, 1 - 2i,\text{ calculate: }\:(z - w)^2
    z - w \:=\:(3+4i) - (1-2i) \;=\;3 + 4i - 1 + 2i \;=\;2 + 6i


    (z\:-\:w)^2 \;=\;(2\:+\:6i)(2\:+\:6i) \;=\;4\:+\:12i\:+\:12i\:+\:36i^2 \;=\;4\:+\:24i\:-\:36 . =\;-32\:+\:24i

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