Q. Write an explicit formula that represents the sequence defined by the following recursive formula:a1=1 and an=−3an−1Answer: an=
Identify Pattern: To find the explicit formula for the sequence, we start by looking at the first few terms to identify a pattern.Given: a1=1Using the recursive formula an=−3an−1, we find the next few terms:a2=−3a1=−3(1)=−3a3=−3a2=−3(−3)=9a4=−3a3=−3(9)=−27We can see that each term is −3 times the previous term, which suggests a geometric sequence with a common ratio of −3.
Explicit Formula: The general form of an explicit formula for a geometric sequence is an=a1⋅r(n−1), where a1 is the first term and r is the common ratio.In our case, a1=1 and r=−3.So, the explicit formula is an=1⋅(−3)(n−1).
Simplify Formula: We simplify the explicit formula to get the final answer. an=(−3)n−1This is the explicit formula for the given recursive sequence.
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