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A bicyclist is riding at a speed of 18 mi/h when she starts down a long hill. The distance d she travels in feet can be modeled by d(t) = 41^2 + 18t, where t is the time
in seconds. How long will it take her to reach the bottom of a 400-foot-long hill?

Respuesta :

Answer:

8 seconds

Step-by-step explanation:

d(t)=400

4t^2+18t=400

4t^2+18t-400=0          subtract 400 from both sides

2t^2+9t-200=0           divide by 2 on both sides

x=8; -25/2                     solve using quadratic formula

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