MHB What is the Value of this Summation?

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The summation evaluates the expression involving square roots and fourth roots of consecutive integers from 1 to 9999. The formula simplifies the terms in the denominator, allowing for easier computation. Participants discuss the convergence and potential numerical value of the summation. The mathematical intricacies highlight the importance of understanding limits and approximations in such series. This analysis emphasizes the value of summation techniques in mathematical problem-solving.
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\[\sum_{n=1}^{9999}\frac{1}{(\sqrt{{n+1}}+\sqrt{n}\,\,)(\sqrt[4]{n+1}\,\,+\sqrt[4]{n}\,\,)}\]
 
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Albert said:
$\sum_{1}^{9999}\dfrac{1}{(\sqrt{{n+1}}+\sqrt{n}\,\,)(\sqrt[4]{n+1}\,\,+\sqrt[4]{n}\,\,)}$

Rationalizing You have...

$\displaystyle \frac{1}{(\sqrt{n+1} + \sqrt{n})\ (\sqrt[4]{n+1} + \sqrt[4]{n})} = \frac{(\sqrt{n+1} - \sqrt{n})\ (\sqrt[4] {n+1} - \sqrt[4] {n})}{\sqrt{n+1} - \sqrt{n}} = \sqrt[4] {n+1} - \sqrt[4] {n}$

... that is a 'telescopic sum'...

$\displaystyle S= \sqrt[4] {2} - \sqrt[4] {1} + \sqrt[4] {3} - \sqrt[4] {2} + ... + \sqrt[4] {10000} - \sqrt[4] {9999} = 10 - 1 = 9$

Kind regards

$\chi$ $\sigma$
 
well done !
 
Here is a little puzzle from the book 100 Geometric Games by Pierre Berloquin. The side of a small square is one meter long and the side of a larger square one and a half meters long. One vertex of the large square is at the center of the small square. The side of the large square cuts two sides of the small square into one- third parts and two-thirds parts. What is the area where the squares overlap?

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