SOLUTION: A water rocket is launched upward with an initial velocity of 48 ft/sec. It's height h, in feet, after t seconds is given by h=48t - 16t^2. After how many seconds will the height o

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Question 315040: A water rocket is launched upward with an initial velocity of 48 ft/sec. It's height h, in feet, after t seconds is given by h=48t - 16t^2. After how many seconds will the height of the rocket be 20 feet?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
+h=48t-16t%5E2=20
16t%5E2-48t%2B20=0
4t%5E2-12t%2B5=0
Factor the quadratic.
+%282t-5%29%282t-1%29=0+
Two solutions:
2t-5=0
2t=5
t=5%2F2
.
.
.
2t-1=0
2t=1
t=1%2F2
.
.
.
The rocket first reaches 20 ft in 1/2 sec going up and then reaches 20 ft in 5/2 sec going down.