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Use the Root Test to determine whether the following series converge. $$1+\left(\frac{1}{2}\right)^{2}+\left(\frac{1}{3}\right)^{3}+\left(\frac{1}{4}\right)^{4}+\dots$$

Short Answer

Expert verified
Question: Determine the convergence of the series \(\sum_{n=1}^{\infty} \left(\frac{1}{n}\right)^{n}\) using the Root Test. Answer: The series \(\sum_{n=1}^{\infty} \left(\frac{1}{n}\right)^{n}\) converges.

Step by step solution

01

Recall the Root Test

The Root Test states that given a series \(\sum_{n=1}^{\infty} a_n\), if \(\lim_{n\to\infty} \sqrt[n]{|a_n|} = L\), then: - If \(L < 1\), the series converges. - If \(L > 1\), the series diverges. - If \(L = 1\), the test is inconclusive. In our case, the series is given by \(a_n = \left(\frac{1}{n}\right)^{n}\).
02

Apply the Root Test

We need to find the limit \(\lim_{n\to\infty} \sqrt[n]{|a_n|}\) for the series. So, we have to find: $$\lim_{n\to\infty} \sqrt[n]{\left|\left(\frac{1}{n}\right)^{n}\right|}$$ Since the terms of the series are positive, we can drop the absolute value signs: $$\lim_{n\to\infty} \sqrt[n]{\left(\frac{1}{n}\right)^{n}}$$
03

Simplify the expression

We can simplify the above expression by using the property \((a^b)^c = a^{bc}\): $$\lim_{n\to\infty} \left(\frac{1}{n}\right)^{n\cdot\frac{1}{n}} = \lim_{n\to\infty} \left(\frac{1}{n}\right)$$
04

Calculate the limit

Now calculate the limit: $$\lim_{n\to\infty} \left(\frac{1}{n}\right) = 0$$ Since \(0\) is less than 1, the Root Test tells us that the series converges.

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Most popular questions from this chapter

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