"we use different formulas to find the distance of a segment on a number line, d=|a−b|, and the distance of a segment in the coordinate plane, d=(x2−x1)2+(y2−y1)2−−−−−−−−−−−−−−−− −−√. why is it necessary to use the absolute value of the difference when finding the distance on a number line, but not necessary when finding the differences of the coordinates in the coordinate plane? "