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Math Help - x + iy

  1. #1
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    x + iy

    just a quick question on expressing (1 + i) ^3 in the form x + iy
    the answer i came to was:
    2 + 4i + i^2 + i^2<br />
                                   = 2 + 4i -1 -1<br />
                                   = 0 + 4i

    however im not sure if this is correct...
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  2. #2
    Behold, the power of SARDINES!
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    Quote Originally Posted by murielx View Post
    just a quick question on expressing (1 + i) ^3 in the form x + iy
    the answer i came to was:
    2 + 4i + i^2 + i^2<br />
= 2 + 4i -1 -1<br />
= 0 + 4i

    however im not sure if this is correct...
    I am not sure how you expanded the above but it can be treated like a polynomial in i.

    Using the binomial theorem or by the distributive law you get

    (1+i)^3=\sum_{n=0}^{3}\binom{3}{n}1^{3-n}i^{n}=1+3i+3i^2+i^3=1+3i-3-i=-2+2i
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