Question 603039
Given equation:
h(t)= -16t2 + 80t +73 
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The basement floor (relative to sea level) is 50-9 = 41 feet
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Set h(t) to 41 and solve for t:
h(t)= -16t2 + 80t +73 
41 = -16t2 + 80t +73 
0 = -16t2 + 80t + 114
0 = -8t2 + 40t + 57
0 = 8t2 - 40t - 57
Solve by the "quadratic formula" to get:
x = {6.2, -1.2}
throw out the negative solution (extraneous) leaving:
x = 6.2 seconds
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details of quadratic formula:
*[invoke quadratic "x", 8, -40, -57 ]