Answer:
4 seconds
Step-by-step explanation:
using the vertex formula of a quadratic,
, where (h,k) is the vertex
h is height and t is time in seconds
the vertex (maximum height) of the dolphin is (h,k) or (0.5, 2)
Height of 1/2
time of 2 seconds
it will take 2 additional seconds to reach the water again.
this can also be solved using quadratic equation, but since it was already set up in vertex form, i'd use that.