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Math Help - Imaginary Numbers

  1. #1
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    Imaginary Numbers

    How do you simplify: (7+15i)-(14-i)


    How do you find the reciprocal of: (-6-7i)/(-3+5i)
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  2. #2
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    \frac{1}{{a + bi}} = \frac{{a - bi}}{{a^2  + b^2 }}
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  3. #3
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    Quote Originally Posted by Plato View Post
    \frac{1}{{a + bi}} = \frac{{a - bi}}{{a^2  + b^2 }}
    What is that supposed to mean to me regarding imaginary numbers?
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    Quote Originally Posted by agentlopez View Post
    How do you find the reciprocal of: (-6-7i)/(-3+5i)
    The reciprocal of any fraction a/b is b/a. (So long as a is not 0.)

    So the reciprocal of
    \frac{-6 - 7i}{-3 + 5i}
    is
    \frac{-3 + 5i}{-6 - 7i}

    Now you need to rationalize this expression. This is what Plato's comment refers to.

    -Dan
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  5. #5
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    Quote Originally Posted by agentlopez View Post
    What is that supposed to mean to me regarding imaginary numbers?
    Perhaps you have misunderstood the purpose of a site such as this one.
    We offer help with problems; we generally do not give instruction.

    You asked for help with reciprocals of complex numbers.
    That is exactly what I gave you.
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