Question 820657: Lauren shot a rocket from her backyard.The equation that models this scenario is y=-16x^2+80x+10. For how long was Laurens rocket above 74 feet?
Answer by TimothyLamb(4379)   (Show Source):
You can put this solution on YOUR website! ---
y = -16x^2 + 80x + 10 = 74
-16x^2 + 80x + 10 = 74
-16x^2 + 80x - 64 = 0
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the above quadratic equation is in standard form, with a=-16, b=80, and c=-64
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to solve the quadratic equation, by using the quadratic formula, copy and paste this:
-16 80 -64
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the two real roots (i.e. the two x-intercepts), of the quadratic are:
x = 1
x = 4
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answer:
the rocket was above 74 feet altitude between 1 second and 4 seconds after launch
so for a total of 3 seconds
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