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Write an explicit formula that represents the sequence defined by the following recursive formula:

a_(1)=5" and "a_(n)=a_(n-1)-3
Answer: 
a_(n)=

Write an explicit formula that represents the sequence defined by the following recursive formula:\newlinea1=5 and an=an13 a_{1}=5 \text { and } a_{n}=a_{n-1}-3 \newlineAnswer: an= a_{n}=

Full solution

Q. Write an explicit formula that represents the sequence defined by the following recursive formula:\newlinea1=5 and an=an13 a_{1}=5 \text { and } a_{n}=a_{n-1}-3 \newlineAnswer: an= a_{n}=
  1. Understand the recursive formula: Understand the recursive formula.\newlineThe given recursive formula is a1=5a_{1}=5 and an=an13a_{n}=a_{n-1}-3. This means that each term is 33 less than the previous term, starting with the first term being 55.
  2. Determine first few terms: Determine the first few terms of the sequence.\newlineTo find the explicit formula, it's helpful to write out the first few terms of the sequence using the recursive formula:\newlinea1=5a_{1} = 5\newlinea2=a13=53=2a_{2} = a_{1} - 3 = 5 - 3 = 2\newlinea3=a23=23=1a_{3} = a_{2} - 3 = 2 - 3 = -1\newlinea4=a33=13=4a_{4} = a_{3} - 3 = -1 - 3 = -4\newline...\newlineWe can see that each term is decreasing by 33 from the previous term.
  3. Look for pattern: Look for a pattern to derive the explicit formula.\newlineFrom the pattern in Step 22, we can see that each term is 33 less than the previous term. This suggests that the nnth term is the first term minus 33 times (n1)(n-1), because there are (n1)(n-1) steps from the first term to the nnth term.
  4. Write explicit formula: Write the explicit formula based on the pattern.\newlineThe explicit formula for the nth term is:\newlinean=a13(n1)a_n = a_1 - 3(n-1)\newlineSince we know a1=5a_1 = 5, we can substitute that into the formula:\newlinean=53(n1)a_n = 5 - 3(n-1)
  5. Simplify formula: Simplify the explicit formula.\newlineNow we simplify the formula:\newlinean=53n+3a_{n} = 5 - 3n + 3\newlinean=83na_{n} = 8 - 3n\newlineThis is the explicit formula for the given recursive sequence.

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