In a quadratic equation that models the height of an object in projectile motion, such as a tennis ball, the general form is often represented as:
\[ h(t) = -at^2 + bt + c \]
where:
- \( h(t) \) is the height of the object at time \( t \),
- \( -a \) is a coefficient representing the effect of gravity,
- \( b \) is the initial velocity of the object,
- \( c \) is the initial height from which the object is launched.
If the equation you are referring to is something like \( h(t) = -at^2 + bt + 4 \), then the "4" represents the initial height \( c \) of the ball in feet. This means that at time \( t = 0 \), the ball was at a height of 4 feet, indicating where Mark hit the ball from (perhaps above ground level).