Arithmetic Sequences and Series

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SUMMARY

The discussion centers on finding the nth term of the arithmetic sequence -5, 0, 5, 10 using the formula un = a + (n-1)d. The correct nth term is derived as un = 5n - 10, but the book states un = 5n, which is contingent on the indexing of the first term. If the first term is indexed at 1, the user's solution is valid; however, if indexed at -1, the book's answer holds true. Clarity on indexing is crucial for accurate results in arithmetic sequences.

PREREQUISITES
  • Understanding of arithmetic sequences and series
  • Familiarity with the formula un = a + (n-1)d
  • Knowledge of indexing in sequences
  • Basic algebraic manipulation skills
NEXT STEPS
  • Study the concept of indexing in sequences and its implications
  • Practice deriving nth terms for various arithmetic sequences
  • Explore the differences between arithmetic and geometric sequences
  • Learn about the applications of arithmetic sequences in real-world scenarios
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Students studying mathematics, educators teaching arithmetic sequences, and anyone looking to clarify concepts related to sequences and series.

odolwa99
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Homework Statement



Just a quick question I was looking to have cross checked…

Q. Find un, the nth term of sequence -5, 0, 5, 10,…


Homework Equations



un = a + (n-1)d

The Attempt at a Solution



-5 + (n-1)5
-5 + 5n - 5
5n-10

The answer in the book, however, indicates that un = 5n. Am I wrong, or are they? Thanks.
 
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Depends. Are we assuming the first term has index 1? 0? -1? 1000?

If the first term has index -1, then the book is right. Your answer is also right, but you want to state that the first term has index 1.
 
I answered two other questions just like it, before this one, and had no problem getting the answer, although the first terms in both of those sequences were positive.

Thanks for the tip, though. I'll mention the index when answering other questions like it in future.
 

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