26. Use the information below to sketch a graph of the polynomial function y = f(x). SEE EXAMPLE 4

• f(x) is positive on the intervals (−∞, −3), (−2, 0),

and (2, 3).

• f(x) is negative on the intervals (−3, −2), (0, 2),

and (3, ∞).

• f(x) is increasing on the interval (−2.67, −1)

and (1, 2.5).

• f(x) is decreasing on the intervals (−∞, −2.67),

(−1, 1), and (2.5, ∞).

27. The equation shown models the average depth y,

in feet, of a lake, x years after 2016, where

0 < x < 6. Use technology to graph the function.

In what year does this model predict a relative

minimum value for the depth?

Depth: y = x^4 -9x^3 + 24x^2 -31x + 66