SOLUTION: The sum of the second and third terms of a geometric progression is six times the fourth term. Find the two possible values of the common ratio.

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Question 1057668: The sum of the second and third terms of a geometric progression is six times the fourth term. Find the two possible values of the common ratio.
Answer by ikleyn(52798) About Me  (Show Source):
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The sum of the second and third terms of a geometric progression is six times the fourth term.
Find the two possible values of the common ratio.
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The condition says

ar+%2B+ar%5E2 = 6ar%5E3

where "a" is the first term and "r" is the common ratio.
It leads to the equation

6r%5E2+-+r+-+1 = 0,  or, in the factorized form

(2r-1)*(3r+1) = 0.

The roots are 1%2F2 and -1%2F3.

It is your answer.