Answer:
Both solutions are valid, and depending on the context of the problem, one or both solutions may be useful in solving for different parameters, such as the maximum height or the time of flight of the projectile.
Explanation:
In a projectile motion formula, such as the one that describes the height of an object in motion as a function of time, there are two solutions because the object can reach the same height at two different times during its trajectory.
The negative solution represents the time it takes for the object to reach its maximum height and then start falling back down to the ground. The positive solution represents the time it takes for the object to reach the same height on its way up.
So, both solutions are valid, and depending on the context of the problem, one or both solutions may be useful in solving for different parameters, such as the maximum height or the time of flight of the projectile.