Ineed an understanding for this problem

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

How do i start to solve? would appreciate a walk-thru! a bird sitting 16ft above the ground in an apple tree dislodges an apple. after how many seconds does the apple land on the ground? (assuming that no branches will interfere with it's fall)

This is about circle theorems. someone asap : (