In a geometric sequence, t1 + t2 + t3 = 21 and t4 + t5 + t6 =168. Find the sequence.

how do u use the formula Sn = a(r^n -1)/r -1) to find the sequence?

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- January 25th 2009, 05:54 PMmegs_worldGeometric sequence
In a geometric sequence, t1 + t2 + t3 = 21 and t4 + t5 + t6 =168. Find the sequence.

how do u use the formula Sn = a(r^n -1)/r -1) to find the sequence? - January 25th 2009, 07:43 PMSoroban
Hellp, megs_world!

Quote:

In a geometric sequence: .

Find the sequence.

how do u use the formula: to find the sequence?

We know the sum of the first 3 terms: .

. . Hence: . .[1]

We know the sum of the first 6 terms: .

. . Hence: . .[2]

Divide [2] by [1]: .

Factor and reduce: .

. . Then: .

Substitute into [1]: .

Therefore, the sequence is: .