Which statement is true about the distance formula, , when describing the distance along a line segment?

It is not a precise definition because it uses variables to represent unknown values.
It is not a precise definition because it uses a square root sign, which means the result might be an irrational number.
It is not a precise definition because it is based on an understanding of point, which is an undefined term.
It is not a precise definition because it is based on an understanding of coordinates, which are defined based on the distance of a line segment.