Answer:
Step-by-step explanation:
At 4 seconds because 4 is the maximum point in the parabola
It's 15 because
3 groups and 5 people in each group
and becomes 15
I HOPE THIS HELPS
Here is an example(i don't really know how to explain)
Answer: after adding them -7r^2+12r-8
Step-by-step explanation: add them