Chapter 10 - Radical Expressions and Equations - Cumulative Test Prep - Short Response - Page 648: 25

1.581 seconds

$h=-16t^2+c$ dropped from height of 40 feet to hit the ground $h=0$ $c=40$ $0=-16t^2+40$ $16t^2=40$ $16t^2/16=40/16$ $t^2=5/2$ $\sqrt {t^2} = \sqrt {5/2}$ $t=1.581$ Usually, we would have -1.581 as another answer. However, we cannot have a negative time. (Thus, -1.581 is an extraneous solution.)