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Geometrical Sequence

Source: 1996 National High School Mathematics League, Exam One, Problem 2

March 3, 2020

ratio

Problem Statement

For geometrical sequence

(a_n)

, the first term

a_1=1536

, common ratio

q=-\frac{1}{2}

. Let

\pi_n=\prod_{i=1}^n a_i

, so the lagerest one in

(\pi_n)

\text{(A)} \pi_9\qquad\text{(B)} \pi_{11}\qquad\text{(C)} \pi_{12}\qquad\text{(D)} \pi_{13}