Q. Find an explicit formula for the geometric sequence −8,−40,−200,−1000,…. Note: the first term should be c(1).c(n)=
Identify pattern and type: Identify the pattern in the sequence and determine if it is arithmetic or geometric.The given sequence is −8,−40,−200,−1000,…To determine if the sequence is arithmetic or geometric, we look at the ratio of consecutive terms.−8−40=5−40−200=5−200−1000=5Since each term is multiplied by the same number to get the next term, the sequence is geometric.
Find first term and common ratio: Find the first term c(1) and the common ratio r of the sequence.The first term c(1) is given as −8.To find the common ratio, we divide the second term by the first term:r=−8−40=5
Write explicit formula: Write the explicit formula for the geometric sequence using c(1) and r.The explicit formula for a geometric sequence is given by:c(n)=c(1)⋅r(n−1)Substitute c(1)=−8 and r=5 into the formula:c(n)=−8⋅5(n−1)
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