Answer
2.8 seconds
Work Step by Step
$h=-16t^2-20t+180$
$0=-16t^2-20t+180$
$0/-4=(-16t^2-20t+180)/-4$
$0=4t^2+5-45$
$x=(-b±\sqrt {b^2-4ac})/2a$
$x=(-5±\sqrt {5^2-4*4*-45})/2*4$
$x=(-5±\sqrt {25+720})/8$
$x=(-5±\sqrt {745})/8$
We are dealing with time, so we want only the positive square root.
$x=(-5±\sqrt {745})/8$
$x=(-5+\sqrt {745})/8$
$x=(-5+27.29)/8$
$x=22.29/8$
$x=2.786$