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The distance d (in feet) that it takes a car to come to a complete stop on dry asphalt can be modeled by d = 0.05s^2 + 1.1s where s is the speed of the car (in miles per hour). A car has 78 feet to come to a complete stop. Find the maximum speed at which the car can travel.

GAMEMASTERX40  Apr 11, 2018

Best Answer 

 #1
avatar+628 
+2

We can already plug in 78 for d in this equation. 

 

78 = 0.05s^2 + 1.1s 

 

After subtracting 78 from both sides, we have:

 

0.05s^2 + 1.1s - 78 = 0.

 

Solving this quadratic, we have: s = 30.0000000000000004, -52.00000000000001

The last time I checked, we can’t go negative speed, so s = 30

 

It is actually 30.000000000000004, but just round it down. 

supermanaccz  Apr 11, 2018
 #1
avatar+628 
+2
Best Answer

We can already plug in 78 for d in this equation. 

 

78 = 0.05s^2 + 1.1s 

 

After subtracting 78 from both sides, we have:

 

0.05s^2 + 1.1s - 78 = 0.

 

Solving this quadratic, we have: s = 30.0000000000000004, -52.00000000000001

The last time I checked, we can’t go negative speed, so s = 30

 

It is actually 30.000000000000004, but just round it down. 

supermanaccz  Apr 11, 2018

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