SOLUTION: Hello, I need help with this problem: The height, in feet, of a rocket t seconds after blast-off is given by a formula h=1260t-16t^2. After how many seconds will the roc

Question 104568: Hello,

I need help with this problem:

The height, in feet, of a rocket t seconds after blast-off is given by a formula h=1260t-16t^2. After how many seconds will the rocket first reach a height of 23,400 feet?

Thank you
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!

Use the quadratic formula,

where
a=-16, b=1260, and c=-23400

and

t=48.75 seconds
t=30 seconds
Since your looking for the first time, pick the earliest time.
t=30 seconds.
Why two answers? First when the rocket is going up and then when the rocket's coming down, as shown in the graph below, with the horizontal axis equal to h=23,400 feet.

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