9514 1404 393
Answer:
78.71 mph
Step-by-step explanation:
You're looking for the solution to ...
d = 88
0.0015r^2 +r = 88
0.0015r^2 +r -88 = 0
Using the quadratic formula*, we find ...
r = (-1 +√(1² -4(0.0015)(-88)))/(2×0.0015)
r = (-1 +√1.528)/0.003 = 0.236123/0.003 = 78.7077
The speed of the car was about 78.71 mph.
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* The quadratic formula will also give a negative answer of about -745 mph, which is not relevant to the situation.
