Answer
a. $t = 6.61$ s
b. $t = 6.89$ s
c. $0 \leq h \leq 1700$, $t \geq 0$
Work Step by Step
a. Solve for $t$ when $h = 1000$. $1000 = -16t^2 + 1700$
$16t^2 = 700, t^2 = 43.75, t = 6.61s$
b. Solve for $t$ when $h = 940$.
$940 = -16t^2 + 1700$
$16t^2 = 760, t^2 = 47.5, t = 6.89s$
c. Technically speaking the domain is all values of $t$ and all $h \leq 1700$ ($1700$ is the vertex and the maximum).
However, reasonably, $h$ would never be negative: $0 \leq h \leq 1700$, and t would not be either, $t \geq 0$
