Expanding Cube Roots: Solving Limits with Maclaurin Series

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The discussion revolves around solving the limit of the expression as x approaches infinity, specifically the difference between the cube roots of x+1 and x. The Maclaurin series is introduced to expand the cube root of x+1, yielding a series that helps in finding the limit. However, confusion arises when attempting to expand the cube root of x, as it leads to undefined terms. A simpler algebraic approach is suggested, confirming that the limit can be solved without complex series expansion. Ultimately, the participants recognize that redefining variables can simplify the problem-solving process.
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A quiz at the end of Steven Krantz's Calculus Demystified includes the following problem:
Find
<br /> \lim_{x \to \infty} [ \sqrt[3]{x+1}<br /> -<br /> \sqrt[3]{x} ]<br />
I see how one can use the Maclaurin series to get
<br /> \sqrt[3]{x+1} = 1 + \frac {x}{3} - \frac {x^2}{9} + \frac {5 x^3}{81} + . . .<br />
but trying it with the cube root of x gives me zero plus an endless series of undefined terms.
Is there a way to expand \sqrt[3]{x} and solve this problem?
 
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But why do you want expand that in series?
Isn't it by simple high school algebra :
ac{2}{3}&plus;%20%28x&plus;1%29^\frac{2}{3}&plus;x^{\frac{1}{3}}%28x&plus;1%29^{\frac{1}{3}}%20}.gif

for x>0?
 
Oh yeah, you're right zoki85 - thanks!

I also just realized that I could simply define y = x + 1, plug in y-1 for all the x's in the series above and there's the answer to my other question. :)
 

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