Question 231484
h = -16t2 + 22t + 20. 
How long does a team captain have to call heads or tails if it must be done while the coin is in the air?
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He has until it hits the ground, at h(t) = 0
-16t2 + 22t + 20 = 0
*[invoke solve_quadratic_equation -16,22,20]
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The solver uses x, that's the time t.
t = 2 seconds.  (Ignore the negative number)