Question 1182040
We need to solve for the time, x, when the height k(x) goes to zero
x^2 - 2x - 8 = 0
This can be factored as (x-4)(x+2) = 0 which has solutions x=4, x=-2
Since the elapsed time can't be negative, we take the positive solution, x=4
Thus, the whale spends the time from x=0 to x=4 seconds under water.
Ans: 4 s