Question 196647
t1 + t2 = √d/4 + d/1090
How deep is the well if this total time is 2.3 s? (Round the answer to the nearest whole number.) 
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2.3 = sqrt(d)/4 + d/1090
sqrt(d)/4 = 2.3 - d/1090
d/16 = 5.29 - 4.6d/1090 + d^2/1090^2
d^2 + 5.29*1090^2 - 4.6d*1090 - d*1090^2/16 = 0
d^2 - d*(5014 + 74256.25) + 6285049 = 0
d^2 - 79270.25d + 6280549 = 0
*[invoke solve_quadratic_equation 1,-79270.25,6280549]
79 feet looks right.