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`sum_(k=1)^(360)((1)/(ksqrt(k+1)+(k+1)sqrt(k)))` is the ratio of two relative prime positive integers m and n. The value of `(m+n)` is equal to

A

43

B

41

C

39

D

37

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The correct Answer is:
To solve the problem, we need to evaluate the sum: \[ S = \sum_{k=1}^{360} \frac{1}{k \sqrt{k+1} + (k+1) \sqrt{k}} \] ### Step 1: Simplify the Denominator We start by factoring out \(\sqrt{k(k+1)}\) from the denominator: \[ S = \sum_{k=1}^{360} \frac{1}{\sqrt{k(k+1)} \left(\sqrt{k} + \sqrt{k+1}\right)} \] ### Step 2: Rationalize the Denominator Next, we rationalize the denominator by multiplying the numerator and denominator by \(\sqrt{k+1} - \sqrt{k}\): \[ S = \sum_{k=1}^{360} \frac{\sqrt{k+1} - \sqrt{k}}{k(k+1) \left(k+1 - k\right)} \] This simplifies to: \[ S = \sum_{k=1}^{360} \frac{\sqrt{k+1} - \sqrt{k}}{k(k+1)(\sqrt{k+1} - \sqrt{k})} \] ### Step 3: Simplify Further The denominator simplifies to: \[ S = \sum_{k=1}^{360} \frac{\sqrt{k+1} - \sqrt{k}}{k(k+1)(\sqrt{k+1} - \sqrt{k})} = \sum_{k=1}^{360} \frac{1}{\sqrt{k(k+1)}} \] ### Step 4: Telescoping Series Recognizing that this forms a telescoping series: \[ S = \sum_{k=1}^{360} \left( \frac{1}{\sqrt{k}} - \frac{1}{\sqrt{k+1}} \right) \] ### Step 5: Evaluate the Series This telescopes down to: \[ S = 1 - \frac{1}{\sqrt{361}} = 1 - \frac{1}{19} = \frac{18}{19} \] ### Step 6: Identify m and n The result \(\frac{18}{19}\) is in the form \(\frac{m}{n}\) where \(m = 18\) and \(n = 19\). Since 18 and 19 are relatively prime, we can proceed to find \(m+n\). ### Step 7: Calculate m+n Thus, we have: \[ m+n = 18 + 19 = 37 \] ### Final Answer The value of \(m+n\) is: \[ \boxed{37} \]
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