SOLUTION: If b is positive, what is the value of b in the geometric sequence 9,a,4,b? Express your answer as a common fraction.

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Question 980366: If b is positive, what is the value of b in the geometric sequence 9,a,4,b? Express your answer as a common fraction.
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
r, common ratio.
4%2F9=r%5E2, and then 9r%5E3=b.

You can finish from the term at index 1 or from the term at index 3. You want the POSITIVE value for r.

r%5E2=4%2F9
r=0%2B-+2%2F3
r=2%2F3

Easiest enough to continue from index of term 3.
4%2A%282%2F3%29=highlight%288%2F3=t%5B4%5D%29=b.