SOLUTION: The first term of a geometric sequence is 9 and the third term is 4. Find the possible values for the second and fourth terms.

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Question 842089: The first term of a geometric sequence is 9 and the third term is 4. Find the possible values for the second and fourth terms.
Answer by fcabanski(1391) About Me  (Show Source):
You can put this solution on YOUR website!
A geometric sequence is a sequence in which a common factor multiplies each term to get to the next.


9x = y


yx = 4


Solve the two equations for x and y.


Substitute 9x for y in the second equation.


9x*x = 4


9x%5E2+=+4


x%5E2+=+4%2F9
x = + or - sqrt%284%2F9%29 = + or - 2/3. Either one works. I'll show -2/3. You can try 2/3 on your own.


9 * -2/3 = 18/3 = -6


-6 * -2/3 = 12/3 = 4


4 * -2/3 = -8/3


Possible sequence: 9, -6, 4, -8/3