Question

Which of the following is the explicit rule for a geometric sequence defined by a recursive formula of for which the first term is 7?

Answer 1

Answer:

  B.  an = 7·13^(n-1)

Step-by-step explanation:

The general form of the explicit rule for a geometric sequence is ...

  an = a1·r^(n-1)

The common ratio (r) is the multiplier in the recursive rule: 13. The first term (a1) is given as 7. Filling in these values, you have ...

  an = 7·13^(n-1)

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As always, you can check the answer choices to see which one satisfies the requirements. Here, you need go no further than evaluating each of the expressions for n=1.

  A. a1 = 13·7² ≠ 7

  B. a1 = 7·1  = 7 . . . . as required

  C. a1 = 7·13² ≠ 7

  D. a1 = 13·1 ≠ 7

Answer 2

.it should be C for the question