we have the quadratic equation
[tex]h=175t-16t^2[/tex]
For h=85 ft
substitute in the given equation
[tex]\begin{gathered} 85=175t-16t^2 \\ 16t^2-175t+85=0 \end{gathered}[/tex]
Solve the quadratic equation
Using the formula
a=16
b=-175
c=85
substitute
[tex]t=\frac{-(-175)\pm\sqrt{-175^2-4(16)(85)}}{2(16)}[/tex][tex]t=\frac{175\pm158.70}{32}[/tex]
the values of t are
t=10.43 sec and t=0.51 sec
Verify with the graph
using a graphing tool
is ok
the answer is
t=0.51 sec and t=10.43 sec
