Given a term in a geometric sequence and the common ratio, find the explicit formula, a11=5120 ans r=-2
1 answer:
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Answer:
(-∞, -2), (-2, -0.618), and (1.618, 3)
Step-by-step explanation:
The red arrows indicate the regions in which the function is decreasing.
The corresponding intervals are (-∞, -0.618) and (1.618, 3),
Let's examine the intervals given.
(-∞, -2): Yes, decreasing.
(-2, -0.618): Yes, decreasing.
(-2, 0.689): No. Decreasing in (-2, -0.618) but increasing in (-0.618, 0.689).
(-1.17, 0.689): No. Decreasing in (-1.17, -0.618) but increasing
in (-0.618, 0.689).
(0.698, 71.457): No. Increasing from (0.698, 1.618), decreasing in (1.618, 3) and increasing in (3, 71.457).
(1.618, 3): Yes, decreasing.
(2.481, ∞): No. Decreasing in (2.481, 3) but increasing in (3, ∞).
The three choices that indicate a decreasing interval are (-∞, -2),
(-2, -0.618), and (1.618, 3).
