Question

How do you do this question?

Answer 1

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).