Question

A model rocket is shot straight up from the roof of a school. The height, h, in meters, after t seconds can be approximated by h(t)=-5t2+22t+15. Answer the following questions algebraically, showing all of your work

How long does it take for the rocket to pass a window that is 10m above the ground? (hint: make h=10, group like terms, then solve the quadratic equation)

Answer 1

Answer:
`(11+√(146))/(5)` seconds

Explanation:

`10=-5t^2 +22t+15\\\\5t^2 -22t-5=0\\\\t=(22 \pm √((-22)^2 -4(5)(-5)))/(2(5))\\\\t=(11+√(146))/(5) \text{ } (t > 0)`