How Accurate Is the Binomial Approximation for Small x Values?

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SUMMARY

The discussion focuses on the accuracy of the binomial approximation for small values of x, specifically demonstrating that the expression 1/(1+x) - √(1-2x) is approximately equal to (3/2)x² when x is sufficiently small. Participants emphasize the importance of expanding both 1/(1+x) and √(1-2x) using the binomial formula and neglecting higher-order terms. The consensus is that for small x, terms involving x³ and higher become negligible, validating the approximation.

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  • Basic knowledge of limits and small value analysis
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Students and educators in mathematics, particularly those studying calculus and approximation methods, as well as anyone interested in the practical applications of binomial expansions in mathematical analysis.

Bucky
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Show that if x is small then

1/(1+x) - root(1-2x) ~= (3/2)x^2


im not sure how to even begin this question. there was a part 1 but i don't think its relevant. Small numbers just confuse me...how small is small in any case?
 
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You titled this "binomial Approximations"- obviously you are intended to expand both [itex]\frac{1}{1+x}= (1+x)^{-1}[/itex] and [itex]\sqrt{1- 2x}= (1-2x)^{\frac{1}{2}}[/itex] using the binomial formula. Then drop higher powers since if x is small, x to a power is much smaller.
"how small is small in any case?" Well, in this case, small enough that the third power is negligible- because you were asked to show that this is approximately a number times x2
 

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