Answer:
5 seconds.
Step-by-step explanation:
The first thing we can do is convert h(x) into 0. -16x²+64x+80=0
Then, factor out -16, as both 64 and 80 are divisible by 16.
This leaves you with x²-4x-5=0.
Then, you factor that expression to get (x+1)(x-5).
Convert those to x+1=0 and x-5=0.
Your answers will be x= -1 and x= 5, but since we cannot have a negative time, 5 is the only correct option.