Algebra 1 math problem?
The equation d=.05rsquared+r models the distance,d, in feet traveled by a car moving r miles per hour (r is the speed of the car) after the driver begins to stop the car. The question is If 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 coefficents A,B, and C and then use the quadradic formula to solve mathematically)
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d = 0.05r^2 + r
Since after applying the brake the car travels 20feet d is 20feet. Putting this in the equation we get
20 = 0.05r^2 + r
=> 0.05r^2 + r - 20 = 0
This is a quadratic equation where A=0.05, B = 1 and C = -20
Value of r is given by (-B +- (sqrt(B^2 - 4AC))) / 2A
Where B^2 means B squared. and sqrt means square root.
Plug in the value and find the speed at which the driver was driving. Discard the negative speed as that holds no significance in real life.