Q. Write an explicit formula that represents the sequence defined by the following recursive formula:a1=−7 and an=an−1−5Answer: an=
Identify Pattern: The recursive formula given is an=an−1−5, with the initial condition a1=−7. To find the explicit formula, we need to determine the pattern of the sequence by looking at the first few terms.
Calculate First Few Terms: Let's calculate the first few terms using the recursive formula:a2=a1−5=−7−5=−12a3=a2−5=−12−5=−17a4=a3−5=−17−5=−22From these calculations, we can see that each term is 5 less than the previous term, which suggests that the sequence is arithmetic with a common difference of −5.
Use Arithmetic Sequence Formula: The nth term of an arithmetic sequence can be found using the formula an=a1+(n−1)d, where a1 is the first term and d is the common difference. In this case, a1=−7 and d=−5.
Substitute Values: Substituting the values of a1 and d into the formula, we get:an=−7+(n−1)(−5)an=−7−5n+5an=−5n−2This is the explicit formula for the given recursive sequence.
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