Unit 6.6, Lesson 9: Practice Problems
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).
Let be the amount of food needed for one man for one day. At the beginning, we have enough food for 400 men for 40 days, i.e.
After 10 days, the 400 men will have consumed
food, impliying that the food remaining is
If 200 more men join the garrison, there are now 600 men. Each of them requires food each day, and there are
units of food remaining. They will last
days.