H= -16t^2 +15t+12 what is Sam’s height after 1 second

Look at the following graph of the given equation. determine whether the equation is a function. explain why or why not.

How do i do this? i don’t understand

Tom wants to order tickets online so that he and three of his friends can go to a water park the cost of the tickets is 16.00 per person there is also a 2.50 one-time service fee for ordering tickets online write an expression in term of n that represents the cost for n ordering tickets online