We are trying to represent the change in position of a bird flying down 7 ft to the ground.
Often, for the y axis- up is positive and down is negative.
Change in position is displacement- how far it was from the starting point
( different from distance which is how far is traveled
ex. doubling back would have distance they traveled some distance while the displacement is 0 because they are back to where they started).
The bird is going down 7 ft from where it originally was, which can be represented by
Bird's displacement = -7 ft