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Homework Help: Binomial theorem

  1. Jun 23, 2012 #1
    1. The problem statement, all variables and given/known data

    Find the first four terms in the expansion of [itex]\left(1-3x\right)^{3/2}[/itex]. By substituting in a suitable value of x, find an approximation to [itex]97^{1/2}[/itex].

    2. Relevant equations

    3. The attempt at a solution

    I used the binomial expansion formula to work the answer and it is 1- 4.5x - (22x2/8) - (247x3/48) + ... .

    Is that correct?

    I did the second part and i got 0.848. What do you think?

    Thanks in advance for any help.
  2. jcsd
  3. Jun 23, 2012 #2
    First two terms are correct, it goes wrong after that. Check your calculations again.
  4. Jun 23, 2012 #3


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    I think that it's slightly off :wink:
    Last edited: Jun 23, 2012
  5. Jun 23, 2012 #4
    The positive square root of 100 is 10, and square root 81 is 9. Where would you expect square root of 97 to lie in? :wink:

    How did you solve this part?
  6. Jun 23, 2012 #5
    Slightly? Wouldn't that be too much? :tongue:
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