A model rocket is launched from the ground. The height h of the rocket

1.	A model rocket is launched from the ground. The height h of the rocket after t seconds from lift off is given by h(t) = -5t2 + 100t; 0 ≤ r ≤ 20. At what time the rocket is 495 feet above the ground?
Answer» h(t) = -5t² + 100t at t = 0, h(0) = 0 at t = 1, h(1) = -5 + 100 = 95 at t = 2, h(2) = -20 + 200 = 180 at t =3, h(3) = -45 + 300 = 255 at t = 4, h(4) = -80 + 400 = 320 at t = 5, h(5) = -125 + 500 = 375 at t = 6, h(6) = – 180 + 600 = 420 at t = 7, h(7) = -245 + 700 = 455 at t = 8, h(8) = – 320 + 800 = 480 at t = 9, h(9) = -405 + 900 = 495 So, at 9 secs, the rocket is 495 feet above the ground.

A model rocket is launched from the ground. The height h of the rocket after t seconds from lift off is given by h(t) = -5t2 + 100t; 0 ≤ r ≤ 20. At what time the rocket is 495 feet above the ground?

Answer»

h(t) = -5t² + 100t

at t = 0, h(0) = 0

at t = 1, h(1) = -5 + 100 = 95

at t = 2, h(2) = -20 + 200 = 180

at t =3, h(3) = -45 + 300 = 255

at t = 4, h(4) = -80 + 400 = 320

at t = 5, h(5) = -125 + 500 = 375

at t = 6, h(6) = – 180 + 600 = 420

at t = 7, h(7) = -245 + 700 = 455

at t = 8, h(8) = – 320 + 800 = 480

at t = 9, h(9) = -405 + 900 = 495

So, at 9 secs, the rocket is 495 feet above the ground.