How Do You Find the Limit of the Series S_n = \dfrac {3}{8}⋅\dfrac {4^n}{3^n}?

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SUMMARY

The limit of the series \( S_n = \frac{3}{8} \cdot \frac{4^n}{3^n} \) diverges to infinity, as confirmed by applying L'Hôpital's rule. The discussion emphasizes the importance of verifying the formula against multiple terms in the sequence, rather than fitting it to just the first two values. A correct approach involves recognizing that the series can also be represented as \( S_n = \frac{n}{1+n} \), which converges to 1 as \( n \) approaches infinity. Thus, the original formula presented was incorrect.

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chwala
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Homework Statement
See attached.
Relevant Equations
Limits
Consider the series below;

1644709958718.png


From my own calculations, i noted that this series can also be written as ##S_n##=##\dfrac {3}{8}##⋅##\dfrac {4^n}{3^n}##. If indeed that is the case then how do we find the limit of my series to realize the required solution of ##1## as indicated on the textbook? I tried taking limits...L Hopital's rule... and still got ##∞## implying divergence. Are we required to solely maintain the series in the pattern indicated on the text and not any other way?

In other words, if one was given a specific question to find the limit of my series ##S_n##=##\dfrac {3}{8}##⋅##\dfrac {4^n}{3^n}##in an exam, then would it be correct to state ##∞##?
 
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Your formula is wrong. You probably fit it to the first two values, and didn't check if it matches anything else.
 
Office_Shredder said:
Your formula is wrong. You probably fit it to the first two values, and didn't check if it matches anything else.
True it is wrong...i ought to have checked if it applies to the sequence ##S_3##...but we could also have
...our series ##\dfrac {1}{2}##, ##\dfrac {2}{3}##, ##\dfrac {3}{4}##,##\dfrac {4}{5},##... as
##S_n##=##\dfrac {n}{1+n}##
Cheers :cool:
 
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Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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