Atoy rocket is launched from a 2.8 m high platform in such a way that its height, h (in meters), after t seconds is given by the equation h equals negative 4.9 t squared plus 18.9 t plus 2.8. how long will it take for the rocket to hit the ground?

3.98 s (approximately 4 s for practical purposes)

Explanation:

1) Equation given:

h(t) = - 4.9 t² + 18.9 t + 2.8

2) The time it will take the rocket fo hit the ground is given doing h (t) = 0

- 4.9 t² + 18.9 t + 2.8 = 0

3) You can solve that equation using the quadratic equation or working the equation to complete squares.

To use the quadratic equation you have a = - 4.9, b = 18.8, and c = 2.8

With that, t = [-18.8 +/- √ ( 18.8² - 4(-4.9)(2.8) ) ] / (2(-4.9) ) = 3.98 s

(I only picked the positive result because the negative does not have physical meaning).