Question 388044
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You have exactly the right idea:

*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -16t^2\ +\ 90t\ +\ 2\ =\ 75]

*[tex \LARGE \ \ \ \ \ \ \ \ \ \ -16t^2\ +\ 90t\ -\ 73\ =\ 0]

Solve the quadratic using the quadratic formula.  You will find two zeros as is typical with quadratic.  The first root is the time when the ball reaches 75 feet on the way up.  The second root is the time when the ball reaches 75 feet high on the way down.

John
*[tex \LARGE e^{i\pi} + 1 = 0]
My calculator said it, I believe it, that settles it
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