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6. Use Limit Comparison Test to determine whether the series is convergent or divergent:

6. Use Limit Comparison Test to determine whether the series is convergent or divergent-example-1
User Gcstr
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1 Answer

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Given the following series:


\sum(3+2n)/((2+n^2)^2)

We will use the limit Comparison Test to determine whether the series is convergent or divergent.

The limit will be as follows:


\begin{gathered} lim_(n\rightarrow\infty)(a_n)/(b_n) \\ a_n=(3+2n)/((2+n^(2))^(2)) \\ b_n=(2n)/(n^4)=(2)/(n^3) \end{gathered}

So, Substitute with (a) and (b) into the limit then calculate the limit:


\begin{gathered} lim_(n\rightarrow\infty)(3+2n)/((2+n^2)^2)*(n^3)/(2) \\ \\ =l\imaginaryI m_{n\operatorname{\rightarrow}\infty}(3n^3+2n^4)/(2(4+4n^2+n^4))=l\imaginaryI m_{n\operatorname{\rightarrow}\infty}(3n^3+2n^4)/(8+8n^2+2n^4) \end{gathered}

Divide both the numerator and the denominator by n⁴ then substitute

n = ∞, so, the result will be:


=(2)/(2)=1

As the value of the limit is finite and positive

So, both the series are convergent or divergent

The series (b) is convergent

So, the given series is convergent

User Franek Madej
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