Answer:
[tex]t = \frac{53}{32}[/tex]
Step-by-step explanation:
[tex]h=\:-16^2+160t[/tex]
[tex]9=\:-16^2+160t[/tex] [tex]substitute[/tex]
[tex]-16^2+160t=9[/tex]
[tex]-256+160t=9[/tex]
[tex]-256+160t+256=9+256[/tex]
[tex]160t=265[/tex]
[tex]\frac{160t}{160}=\frac{265}{160}[/tex]
[tex]t=\frac{53}{32}[/tex]
At [tex]\frac{53}{32}[/tex] seconds it is at a height of 9 ft.
