SOLUTION: The function D(t)=12t^2-140t gives the distance a car going a certain speed will skid in t seconds. Find the time it would take for the car to skid 180 feet. The time to skid 18

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Question 808245: The function D(t)=12t^2-140t gives the distance a car going a certain speed will skid in t seconds. Find the time it would take for the car to skid 180 feet.
The time to skid 180 feet is ____ seconds. (round to nearest tenth).

how would I set up the problem so I can get the right answer?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
The function D(t)=12t^2-140t gives the distance a car going a certain speed will skid in t seconds. Find the time it would take for the car to skid 180 feet.
The time to skid 180 feet is ____ seconds. (round to nearest tenth).
:
This means D(t) = 180, therefore:
12t^2 - 140t = 180
12t^2 - 140t - 180 = 0
simplify, divide by 4
3t^2 - 35t - 45 = 0
Using the quadratic formulat, I got a positive:
t = 12.835 ~ 12.8 seconds