Question

After his final exam, a student goes to the top of a building and throws his book into the air. The height h in feet of the book above the ground is given by: h = −16t 2 + 32t + 128. How long is the book in the air?

Answer 1

it ceases being in the air when it hits the ground. hits the ground when
\[h=0\] so set
\[-16t^2+32t+128=0\] and solve for t

Answer 2

i would divide first by -16 to solve
\[t^2-2t-8=0\]
\[(t+2)(t-4)=0\]
\[t=4\]