SOLUTION: What is the fifth term in the geometric sequence which begins 2, - 1, 1/2?

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Question 392757: What is the fifth term in the geometric sequence which begins 2, - 1, 1/2?
Found 2 solutions by ewatrrr, solver91311:
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!


Hi

 geometric sequence { 2, - 1, 1/2...} r = -(1/2)

a%5Bn%5D+=+a%5B1%5D%2Ar%5E%28n-1%29

Note: a%5B3%5D+=+2%2Ar%28-1%2F2%29%5E2 = 2/4 = 1/2



a%5B5%5D+=+2%2A%28-1%2F2%29%5E%284%29+=+2%2F16+ =  1/8

Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!


To get from 2 to -1, you had to multiply by -1/2. To get from -1 to 1/2, you had to multiply by -1/2. Clearly, the common ratio is -1/2. So, the 4th term has to be 1/2 times -1/2 = -1/4, and the fifth term is -1/2 times that...


John

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