SOLUTION: Write the first five terms of the geometric sequence. Find the common ratio and write the nth term of the sequence as a function of n. a1 = 18, ak + 1 = −2/5ak Common rat

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Question 1178529: Write the first five terms of the geometric sequence. Find the common ratio and write the nth term of the sequence as a function of n.

a1 = 18, ak + 1 = −2/5ak
Common ratio=
an=
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


Using "a1" to denote the first term is poor form. Use a(1) or a[1] or something like that.

The form gets really bad when you try to write "ak + 1" for the (k+1)th term. Use a(k+1) or a[k+1].

The statement (in better form) "a(k+1) = (-2/5)a(k)" means each term is found by multiplying the previous term by (-2/5). That tells you what the common ratio is.

The n-th term of a geometric sequence is the first term, multiplied by the common ratio (n-1) times: a(n) = a(1)*r^(n-1).

You can do the minimal amount of work to find the answers to your questions.