SOLUTION: A model rocket is launched from the roof of a building. Its flight path through the air is modelled by h(t)=-5t2+30t+10, where h(t) is the height of the rocket above the ground in

Question 1174255: A model rocket is launched from the roof of a building. Its flight path through the air is modelled by h(t)=-5t2+30t+10, where h(t) is the height of the rocket above the ground in metres and t is the time after launch in seconds. I've done all the questions for this question, except these two.
1. How high is this building?
2. When is this rocket 45m of the ground?
Answer by ikleyn(52798) (Show Source): You can put this solution on YOUR website!
.

Question 1)

The height of the building is the constant term of the given quadratic function.


Indeed, it is the height, where the "model rocket" starts at t= 0.


Substitute t= 0 into the formula for the height, and you will get  h(0) = 10 meters.

Question 1 is just answered.

Question 2

To answer this question, solve this quadratic equation


    -5t^2 + 30t + 10 = 45  meters.


You will get two solutions for "t": one works for the rocket moving up, while the other works for falling rocket.

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To learn everything about this class of problems, look into the lessons
    - Introductory lesson on a projectile thrown-shot-launched vertically up
    - Problem on a projectile moving vertically up and down
    - Problem on an arrow shot vertically upward
    - Problem on a ball thrown vertically up from the top of a tower
    - Problem on a toy rocket launched vertically up from a tall platform

Consider these lessons as your textbook, handbook, tutorials and (free of charge) home teacher.
Read them attentively and learn how to solve this type of problems once and for all.

Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this textbook under the topic "Projectiles launched/thrown and moving vertically up and dawn".

Save the link to this online textbook together with its description

Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson

to your archive and use it when it is needed.

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