Q. Write an explicit formula for an, the nth term of the sequence 3,−12,48,…Answer: an=
Identify Pattern in Sequence: The first step is to identify the pattern in the sequence. We notice that each term is multiplied by −4 to get the next term. This indicates that the sequence is geometric with a common ratio of −4.
Calculate nth Term Formula: The first term of the sequence, a1, is 3. Since this is a geometric sequence, the nth term is given by the formula an=a1×r(n−1), where r is the common ratio.
Substitute Values into Formula: Substituting the known values into the formula, we get an=3×(−4)(n−1).
Check Formula with First Terms: We should check the formula with the first few terms to ensure there are no mistakes. For n=1, an=3×(−4)1−1=3×1=3, which matches the first term of the sequence. For n=2, an=3×(−4)2−1=3×(−4)=−12, which matches the second term of the sequence. For n=3, an=3×(−4)3−1=3×16=48, which matches the third term of the sequence. The formula appears to be correct.
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