Chapter 9 - Quadratic Functions and Equations - 9-4 Factoring to Solve Quadratic Equations - Practice and Problem-Solving Exercises - Page 559: 38

a) $h = -16t^2+38t+5$ b) 2.5 seconds

b) $h = -16t^2+38t+5$ $0 = -16t^2+38t+5$ $-16t^2+40t-2t+5 = 0$ $-16t(t-2.5)-2(t-2.5) = 0$ $(-16t-2)(t-2.5)=0$ $-16t-2 = 0$ $-16t-2 +16t = 0+16t$ $-2 = 16t$ $-2/16 = 16t/16$ $-1/8 = t$ $t-2.5=0$ $t-2.5 +2.5 = 0+2.5$ $t = 2.5$