Binomial Theorem: Find Expansion & Approximation of 97^(1/2)

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Homework Help Overview

The problem involves finding the first four terms in the expansion of (1-3x)^(3/2) using the binomial theorem and then using a suitable value of x to approximate 97^(1/2).

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of the binomial expansion formula and question the accuracy of the calculated terms. There is also exploration of the approximation for 97^(1/2) and its relation to known square roots.

Discussion Status

Some participants have provided feedback on the accuracy of the terms calculated, indicating that the first two terms are correct but subsequent terms may contain errors. There is ongoing discussion about the approximation value obtained and its proximity to expected results.

Contextual Notes

Participants are considering the implications of the approximation in relation to known square roots, specifically questioning where the square root of 97 would lie between the square roots of 81 and 100.

naden1
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Homework Statement



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

Homework Equations



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.
 
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naden1 said:
I used the binomial expansion formula to work the answer and it is 1- 4.5x - (22x2/8) - (247x3/48) + ... .

First two terms are correct, it goes wrong after that. Check your calculations again.
 
naden1 said:
I did the second part and i got 0.848. What do you think?

I think that it's slightly off :wink:
 
Last edited:
naden1 said:
I did the second part and i got 0.848. What do you think?

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?
 
Mentallic said:
I think that it's a slightly off :wink:

Slightly? Wouldn't that be too much? :-p
 

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