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1.4.9 Geometric sequences and series (A-level only)

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Question 6

In a geometric progression, the second term is 4 and the sum of all terms is 25.

a.

Find the two possible values of the common ratio rrr.

[3]
b.

Find the corresponding two possible values of the first term aaa.

[2]
c.

Given that r r\,r takes the larger of the two possible values, find the smallest value of n n\,n for which Sn>24.5S_n > 24.5Sn​>24.5.

[3]

1.4.9 Geometric sequences and series (A-level only) Questions

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