SOLUTION: can you please help me solve this equation?! If the distance the car traveled after applying the brakes equals 20 feet, what does that mean to the officer investigating the ac

Question 189123: can you please help me solve this equation?!

If the distance the car traveled after applying the brakes equals 20 feet, what does that mean to the officer investigating the accident? (HINT: Let d = 20, bring 20 to the right so that the equation equals zero, identify the coefficients, A, B and C and then use the quadratic formula to solve mathematically)
a.The car was stopped when the driver applied the brakes
b.The car was going about 12.36 miles per hour
c.The car was going about 32.36 miles per hour
d.There is not enough information to determine the correct answer.

Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
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the quadratic is
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If the distance the car traveled after applying the brakes equals 20 feet, what does that mean to the officer investigating the accident? (HINT: Let d = 20, bring 20 to the right so that the equation equals zero, identify the coefficients, A, B and C and then use the quadratic formula to solve mathematically)
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d(r) = 0.05r^2+r
20 = 0.05r^2+r
Rearrange:
0.05r^2 + r - 20 = 0
Multiply thru by 100 to get rid of the decimal:
5r^2 + 100r - 2000 = 0
Divide thru by 5 to get:
r^2 + 20r - 400 = 0
Use the quadratic formula:
r = [-20 +- sqrt(20^2 -4*-400]/2
r = [-20 +- 44.72]/2
Positive solution:
r = 12.36 mph
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a.The car was stopped when the driver applied the brakes
b.The car was going about 12.36 miles per hour
c.The car was going about 32.36 miles per hour
d.There is not enough information to determine the correct answer.
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Cheers,
Stan H.
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