9514 1404 393
Answer:
5 seconds
Explanation:
You want the positive value of x when y = 0.
0 = -18x² +90x
0 = -18(x)(x -5) . . . . . factor
x = 0 or 5 . . . . . values that make the factors zero
The ball will return to the ground after 5 seconds.
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