Since a real line is a one-dimensional object, the distance between two points uses a variation of the formula for the distance between two points shown above. The formula to calculate the distance between two points on a real line, a and b, is d = |b – a|. Let’s use the formula above to see how this formula is derived. Starting with the formula above: d=\\sqrt{\\left ( b – a \\right ) ^{2}} Since there is only a single dimension, the square of the difference is the only information needed under the radical. This can be further simplified to: d=\\left | b – a \\right | So, that’s why the formula d = |b – a| is used for the distance between points on a one-dimensional line.