SOLUTION: Find the tenth term of a geometric sequence if the third term is 24 and the fifth term is 32/3.

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Question 1150464: Find the tenth term of a geometric sequence if the third term is 24 and the fifth term is 32/3.
Found 2 solutions by josgarithmetic, ikleyn:
Answer by josgarithmetic(39620) About Me  (Show Source):
You can put this solution on YOUR website!
n=3 term, 24

n=5 term, 32/3

r, the common ratio to each successive term
24%2Ar%5E2=32%2F3

r%5E2=%2832%2F3%29%281%2F24%29
r%5E2=%282%2A2%2A2%2A2%2A2%29%2F%283%2A2%2A2%2A2%2A3%29
r%5E2=%282%2A2%29%2F%283%2A3%29

r=2%2F3
You can finish from this.

Answer by ikleyn(52803) About Me  (Show Source):
You can put this solution on YOUR website!
.

            The "solution" by @josgarithmetic, giving the unique value of  2%2F3  to the common ratio,  is  UNCOMPLETED,
            and,  therefore,  INCORRECT.

            I came to bring the correct solution.


a%5B3%5D = 24

a%5B5%5D = 32%2F3


a%5B5%5D%2Fa%5B3%5D = r^2 = %28%2832%2F3%29%29%2F24 = 32%2F72 = 4%2F9, where r is the common ratio of the progression.


Therefore,  the common ratio r may have TWO possible values,  r = 2%2F3  and  r = -2%2F3.

Therefore, looking for a%5B10%5D, we should consider TWO cases.


Case 1.   r = 2%2F3.    Then  a%5B10%5D = a%5B5%5D%2Ar%5E5 = %2832%2F3%29%2A%282%5E5%2F3%5E5%29 = 2%5E10%2F3%5E6.


Case 2.   r = - 2%2F3.    Then  a%5B10%5D = a%5B5%5D%2Ar%5E5 = %2832%2F3%29%2A%28-2%5E5%2F3%5E5%29 = - 2%5E10%2F3%5E6.


ANSWER.  Under given conditions,  the 10-th term,  a%5B10%5D,  may have one of the two values

         a%5B10%5D = 2%5E10%2F3%5E6   or   a%5B10%5D = - 2%5E10%2F3%5E6.

Solved.