Answer:
4 years
Explanation:
To find out when the stock reaches at least $25.40, we need to solve the equation P(x) = -0.1x³ + 3.25x² - 10x + 20 for x when P(x) is greater than or equal to $25.40.
To do this, use a graphing calculator to graph function P(x) and y = 25.4 (attached).
The point of intersection of P(x) and y = 25.4 in the domain 0 ≤ x ≤ 8 (the first 8 years) is (3.982, 25.4).
Therefore, P(x) is greater than or equal to $25.40 when x ≥ 3.982 (3 d.p.) in the domain 0 ≤ x ≤ 8.
As x represents the number of years, and the year is always rounded up to the next year, this means that the stock reaches at least $25.40 in the fourth year.