Q. Write an explicit formula that represents the sequence defined by the following recursive formula:a1=80 and an=−41an−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. We know the first term is a1=80.
Find Second Term: Now we apply the recursive formula to find the second term: a2=−41a1=−41×80=−20.
Find Third Term: Next, we find the third term using the recursive formula: a3=−(41)a2=−(41)×(−20)=5.
Find Fourth Term: We continue this process to find the fourth term: a4=−41a3=−41×5=−1.25.
Determine Geometric Sequence: From these calculations, we can see that each term is −41 times the previous term. This is a geometric sequence with the first term a1=80 and a common ratio r=−41.
Apply Explicit Formula: The explicit formula for a geometric sequence is given by an=a1×r(n−1). Substituting the values we have, we get an=80×(−41)(n−1).
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