Question 748269
h=-4.9t^2-21t+110
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h(t) = -4.9t^2 - 21t + 90 It starts at 90 m high, h(0) = 90, not 110
h(t) = -4.9t^2-21t + 90 = 60 solve for t
-4.9t^2 - 21t + 30 = 0
*[invoke solve_quadratic_equation -4.9,-21,30]
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Ignore the negative solution
t = 1.13 seconds