$$\color{rgb(0,0,0)}1$$

$$\color{rgb(255,0,0)}\begin{array}{l} {\text{AB = }\left| b-a \right| = \left| - 4.8 \right| = 4.8 } \\ {\text{Ou encore }} \\ {\text{AB = }\left| a-b \right| = \left| 4.8 \right| = 4.8 } \end{array}$$