$$\color{rgb(0,0,255)}a$$

$$\color{rgb(0,0,255)}b$$

$$\color{rgb(127,0,0)} \begin{array}{l} {a>b } \\ {\left| a \right|<\left| b \right|} \end{array}$$

$$\color{rgb(0,0,255)}\Rightarrow \text{Variations sur }[0;+\infty[$$

$$\color{rgb(0,0,255)}\Rightarrow \text{Variations sur }]-\infty;0]$$

$$\color{rgb(0,0,255)}\left| a \right|$$

$$\color{rgb(0,0,255)}\left| b \right|$$

$$\color{rgb(255,102,102)}y=\left| x \right|$$