Q. Write an explicit formula that represents the sequence defined by the following recursive formula:a1=5 and an=an−1−3Answer: an=
Understand the recursive formula: Understand the recursive formula.The given recursive formula is a1=5 and an=an−1−3. This means that each term is 3 less than the previous term, starting with the first term being 5.
Determine first few terms: Determine the first few terms of the sequence.To find the explicit formula, it's helpful to write out the first few terms of the sequence using the recursive formula:a1=5a2=a1−3=5−3=2a3=a2−3=2−3=−1a4=a3−3=−1−3=−4...We can see that each term is decreasing by 3 from the previous term.
Look for pattern: Look for a pattern to derive the explicit formula.From the pattern in Step 2, we can see that each term is 3 less than the previous term. This suggests that the nth term is the first term minus 3 times (n−1), because there are (n−1) steps from the first term to the nth term.
Write explicit formula: Write the explicit formula based on the pattern.The explicit formula for the nth term is:an=a1−3(n−1)Since we know a1=5, we can substitute that into the formula:an=5−3(n−1)
Simplify formula: Simplify the explicit formula.Now we simplify the formula:an=5−3n+3an=8−3nThis is the explicit formula for the given recursive sequence.
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