Question 941528: I am having trouble setting up the quadratic equation from this word problem.
A missile fired straight up into the air has a height, in meters, given by h=-5t^2+15t, where t is the time, in seconds, the missle has been in the air. By setting up and solving an equation, find the time when the missle hits the ground.
after_____seconds
Found 2 solutions by nerdybill, josgarithmetic:
Answer by nerdybill(7384)   (Show Source):
You can put this solution on YOUR website! A missile fired straight up into the air has a height, in meters, given by h=-5t^2+15t, where t is the time, in seconds, the missle has been in the air. By setting up and solving an equation, find the time when the missle hits the ground.
after_____seconds
.
Since"h" is the height, when the missile hits the ground, h should be zero.
Our equation:
0 = -5t^2+15t
factor the right
0 = (-5t)(t-3)
t = {0, 3}
throw out the 0, this represents when the missile was fired.
Answer: 3 seconds
Answer by josgarithmetic(39630)  (Show Source):
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