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Sequences and series
Paper 1 · Sequences and series
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A geometric series has sum to infinity
12
12
12
. The sum of its first two terms is
9
9
9
. What are all the possible values of the first term?
A
6
6
6
only
B
18
18
18
only
C
6
6
6
or
18
18
18
D
−
6
-6
−
6
or
18
18
18
E
12
−
6
3
12 - 6\sqrt{3}
12
−
6
3
or
12
+
6
3
12 + 6\sqrt{3}
12
+
6
3
Hint
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