I'm working with some infinite series problems and I have to show that the series
∞∑n=12n2−13n5+2n+1 converges or diverges. I don't have a lot of experience doing this yet, and this is a problem that my teacher made up so I have no way to check my answer.
For this problem, I said the series converges by direct comparison with 23⋅∞∑n=11n3 which converges by the p-series test. However, I'm not sure if I did this correctly and if all of the steps I took were "legal". This is my reasoning:
2n2−13n5+2n+1≤2n23n5 for all n.
bn=2n23n5=23n3
∞∑n=123n3=23⋅∞∑n=11n3 which converges by the p-series test.
Therefore, ∞∑n=12n2−13n5+2n+1 converges by the direct comparison test with ∞∑n=11n3.
Could anyone verify I used the test correctly or point out my mistakes? Thank you.
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