SOLUTION: The formula D=0.054x^2+0.058x describes the distance in feet that it takes to stop a vehicle traveling x miles per hour on dry pavement. How fast can you drive if you wish to be

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Question 739436: The formula D=0.054x^2+0.058x describes the distance in feet that it takes to stop a vehicle traveling x miles per hour on dry pavement.
How fast can you drive if you wish to be able to stop your car within 65 feet?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
The formula D=0.054x^2+0.058x describes the distance in feet that it takes to stop a vehicle traveling x miles per hour on dry pavement.
How fast can you drive if you wish to be able to stop your car within 65 feet?
:
.054x^2 + .058x = 65
A quadratic equation
.054x^2 + .058x - 65 = 0
Use the quadratic formula
x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+
In this equation, a=.054, b=.058, c=-65
x+=+%28-.058+%2B-+sqrt%28.058%5E2-4%2A.054%2A-65+%29%29%2F%282%2A.054%29+
:
x+=+%28-.058+%2B-+sqrt%28.003364%2B14.04+%29%29%2F%28.108%29+
:
x+=+%28-.058+%2B-+sqrt%2814.04673+%29%29%2F%28.108%29+
the positive solution is all we want here
x+=+%28-.058+%2B+3.7479%29%2F%28.108%29+
x = 3.69%2F.108
x = 34.167 mph for a stopping distance of 65 ft