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Homework Help: Am I doing these correct?

  1. Dec 2, 2008 #1
    1. Rationalize the numerator sqrt(5)+3/-4sqrt(7).


    (sqrt(5) + 3) / (-4)(sqrt(7)) =
    (sqrt(5) + 3)(sqrt(5) - 3) / (-4)(sqrt(7))(sqrt(5) - 3) =
    (5 - 9) / (-4)(sqrt(7))(sqrt(5) - 3) =
    -4 / (-4)(sqrt(7))(sqrt(5) - 3) =
    1 / (sqrt(7))(sqrt(5) - 3)

    2. Perform the operation. Write the answer in a + bi form. 3+i/6-i I do this problem and I get the answer (17+9i)/37 is that right?

    (3 + i) / (6 - i) =
    (3 + i)(6 + i) / (6 - i)(6 + i) =
    18 + 9i -1 / 36 + 1
    17 + 9i / 37
     
  2. jcsd
  3. Dec 2, 2008 #2

    LowlyPion

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    Looks OK to me.
     
  4. Dec 2, 2008 #3
    Well I keep submitting then into my homework and I still get them wrong. I don't know what else to do.
     
  5. Dec 2, 2008 #4

    LowlyPion

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    Your denominator in 1) should probably combine the √5*√7 as √35
     
  6. Dec 2, 2008 #5

    LowlyPion

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    In 2) it asks for the answer in the form C = a + b*i

    Hence = 17/37 + (9/37)*i
     
  7. Dec 2, 2008 #6
    oh ok thanks! It worked.
     
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