+956 A model rocket is launched off the top of a platform. The height of the rocket is given by the function h(t) = -4.9t2 + 86t + 2.1, where h(t) is the height in metres and t is the time in seconds.
a) When will the rocket’s height be 200 m?
b) How long will it take for the rocket to reach the ground?
+128472 a) 200 = -4.9t^2 + 86t + 2.1 subtract 200 from both sides
0 = -4.9t^2 + 86t - 197.9 using the quadratic formula.....we have
t = [ -86 ± √ [ (86)^2 - 4 ( -4.9) (-197.9) ] ] / (2 * - 4.9)
Evaluating this.....we have that .... t ≈ 2.7 seconds and t ≈ 14.8 seconds
b) 0 = -4.9t^2 + 86t + 2.1
Again, using the quadratic formula we have ≈ 17.575 seconds
