Question

An arrow is fired into the air with an initial upward velocity of 64 feet per second from the top of a building 80 feet high.

The equation that gives the hight of the arrow at any time t is h = 80 +64t-16t^2 Find the times at which the arrow
will be 128 feet in the air?

Answer 1

128 = 80 + 64 t - 16 t^2

8 = 5 + 4 t - t^2

3 = t (4 - t)

Inspection shows the equation is solved if

t = 1 and t = 3

Plug into original equation to check