Hi. i need on this question . you!

1mile equals approximately 1.6 kilometers. which best approximates the number of miles in 6 kilometers?

The height of a flare fired from the deck of a ship in distress can be modeled by h(t)= -2(8t^2-52t-28), where h is the height of the flare above water and t is the time in seconds. a. find the time it takes the flare to hit the water.

[10 points, algebra 2]according to my answer key the restrictions are -1 and 4. but why not positive 1?