Answer: 9 seconds
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Explanation:
The height will be zero when the object hits the ground. So we need to find the x value(s) that make h(x) = 0 true.
h(x) = 0
-5(x+1)(x-9) = 0
x+1=0 or x-9=0 <--- use zero product property
x=-1 or x=9
The value x represents the time in seconds. Having x = -1 seconds makes no sense, so we ignore that value entirely. The only practical solution is x = 9.
After 9 seconds, the object will have a height of 0. This means the object will hit the ground at the 9 second mark.
