Answer:
At 3 seconds and again at 5 seconds
Step-by-step explanation:
h = -16t² + 128t + 320
560 = -16t² + 128t + 320
16t² - 128t + 240 = 0
t² - 8t + 15 = 0
t² - 5t - 3t + 15 = 0
t(t - 5) - 3(t - 5) = 0
(t - 5)(t - 3) = 0
t = 3, t = 5
3 seconds and 5 seconds
Let the function equal 560 ft
560=-16t^2+128t+320
Subtract 560 from each side
560-560=-16t^2+128t+320-560
0 =-16t^2+128t-240
Divide each side by -16
0/-16 = (-16t^2+128t-240)/-16
0 = t^2 -8t-15
Factor
0=(t-5)(t-3)
Using the zero product property
t-5 =0 t-3=0
t=5 t=3
N=-5
<em>the answer is K for #9</em>
