Integral Test for Convergence of an Infinite Series
Key Questions
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Well, I would avoid using the integral test since evaluating an integral can be very difficult. If nothing else works and you know how to evaluate the integral, then go for it.
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By Integral Test,
#sum_{n=1}^infty 1/n^5# converges.Let us look at some details.
Let us evaluate the corresponding improper integral.
#int_1^infty 1/x^5 dx# #=lim_{t to infty}int_1^tx^{-5} dx# #=lim_{t to infty}[x^{-4}/-4]_1^t# #=-1/4lim_{t to infty}[1/x^4]_1^t# #=-1/4 lim_{t to infty}[1/t^4-1]# #=-1/4(0-1)=1/4# Since the integral
#int_1^infty 1/x^5 dx# converges to
#1/4# ,#sum_{n=1}^infty 1/n^5# also converges by Integral Test.
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Integral Test
If
#f# is a function such that#f(n)=a_n# , then#sum_{n=1}^inftya_n# and#int_1^infty f(x)dx# converge or diverge together.
I hope that this was helpful.
Questions
Tests of Convergence / Divergence
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Geometric Series
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Nth Term Test for Divergence of an Infinite Series
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Direct Comparison Test for Convergence of an Infinite Series
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Ratio Test for Convergence of an Infinite Series
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Integral Test for Convergence of an Infinite Series
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Limit Comparison Test for Convergence of an Infinite Series
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Alternating Series Test (Leibniz's Theorem) for Convergence of an Infinite Series
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Infinite Sequences
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Root Test for for Convergence of an Infinite Series
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Infinite Series
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Strategies to Test an Infinite Series for Convergence
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Harmonic Series
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Indeterminate Forms and de L'hospital's Rule
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Partial Sums of Infinite Series