Q. Use the initial term and the recursive formula to find an explicit formula for the sequence a. Write your answer in simplest form. a=21a=a−2a = ______
Start with Initial Term: The initial term of the sequence is given as a=21. This is the starting point of our sequence.
Define Recursive Formula: The recursive formula given is a=a−2, which means each term is 2 less than the previous term. However, this recursive formula is not properly defined. A recursive formula should relate the term an to a(n−1). Let's assume the correct recursive formula is an=a(n−1)−2, where n represents the position in the sequence.
Find Explicit Formula: To find the explicit formula, we need to express the nth term an in terms of the initial term and n. Since the sequence decreases by 2 each time, we can write the explicit formula as an=a1−2(n−1), where a1 is the first term of the sequence.
Substitute Initial Term: Substitute the initial term a1=21 into the explicit formula to get an=21−2(n−1).
Simplify Explicit Formula: Simplify the explicit formula by distributing the −2 across the (n−1) term: an=21−2n+2.
Combine Like Terms: Combine like terms to get the final explicit formula: an=23−2n.
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