SOLUTION: A firecracker is fired straight up into the air out of a window of a building. Its height, in meters, is given by h = -5 t^2 + 15 t + 100, where t is the time, in seconds, the firc

Question 864482: A firecracker is fired straight up into the air out of a window of a building. Its height, in meters, is given by h = -5 t^2 + 15 t + 100, where t is the time, in seconds, the fircracker has been in the air.
By setting up and solving an equation, find the time(s) when it reaches a height of 10 meters
Answer by LinnW(1048) (Show Source): You can put this solution on YOUR website!

Set h = 10

add -10 to each side

multiply by -1

divide by 5

factor

Possible values for t are 6 and -3
So the firecracker has been in the air 6 seconds.
RELATED QUESTIONS
A firecracker is fired straight up into the air out of a window of a building. Its... (answered by lwsshak3)

Quadratic equation hidden in a word problem. A firecracker is fired straight up into... (answered by MathLover1)

A firecracker is fired straight up into the air out of a window of a building. Its... (answered by DrBeeee)

A missile fired straight up into the air has a height, in meters, given by h = -5 t^2 +... (answered by mananth)

A missile fired straight up into the air has a height, in meters, given by h = -5 t^2 +... (answered by richwmiller)

A missile fired straight up into the air has a height, in feet, given by h = -16 t^2 + 64 (answered by solver91311)

I am having trouble setting up the quadratic equation from this word problem. A... (answered by nerdybill,josgarithmetic)

If a rocket is fired vertically into the air with a speed of 368 feet per second, its... (answered by nerdybill)

A projectile is fired vertically upward and its height h in meters after t seconds is... (answered by Shin123)