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Write an explicit formula that represents the sequence defined by the following recursive formula:

a_(1)=7" and "a_(n)=5a_(n-1)
Answer: 
a_(n)=

Write an explicit formula that represents the sequence defined by the following recursive formula:\newlinea1=7 and an=5an1 a_{1}=7 \text { and } a_{n}=5 a_{n-1} \newlineAnswer: an= a_{n}=

Full solution

Q. Write an explicit formula that represents the sequence defined by the following recursive formula:\newlinea1=7 and an=5an1 a_{1}=7 \text { and } a_{n}=5 a_{n-1} \newlineAnswer: an= a_{n}=
  1. Identify Base Case: Identify the base case and the recursive step from the given recursive formula.\newlineThe base case is a1=7a_{1} = 7, which means the first term of the sequence is 77. The recursive step is an=5an1a_{n} = 5a_{n-1}, which means each term is 55 times the previous term. This indicates that the sequence is geometric with a common ratio of 55.
  2. Write First Few Terms: Write the first few terms of the sequence using the recursive formula to observe the pattern.\newlinea1=7a_{1} = 7\newlinea2=5a1=5×7=35a_{2} = 5a_{1} = 5 \times 7 = 35\newlinea3=5a2=5×35=175a_{3} = 5a_{2} = 5 \times 35 = 175\newlinea4=5a3=5×175=875a_{4} = 5a_{3} = 5 \times 175 = 875\newlineWe can see that each term is 55 times the previous term, confirming that the sequence is geometric.
  3. Derive Explicit Formula: Derive the explicit formula for the geometric sequence.\newlineFor a geometric sequence, the nth term is given by an=a1rn1a_n = a_1 \cdot r^{n-1}, where a1a_1 is the first term and rr is the common ratio. In this case, a1=7a_1 = 7 and r=5r = 5. Therefore, the explicit formula is an=75n1a_n = 7 \cdot 5^{n-1}.

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