a) |-3x+1| [tex]\geq[/tex] 3
b) |x-2| [tex]\leq[/tex] 4
a) [tex]\left | -3x+1 \right |\geq 3\Leftrightarrow \begin{bmatrix} -3x+1\geq 3 & & \\ -3x+1\leq -3 & & \end{bmatrix}\Rightarrow ...[/tex]
b) [tex]\left | x-2 \right |\leq 4\Leftrightarrow -4\leq x-2\leq 4\Rightarrow ...[/tex]
Bạn để ý chút: [tex]\left | A \right |\geq B\Leftrightarrow \begin{bmatrix} A\geq B & & \\ A\leq -B & & \end{bmatrix}[/tex]
[tex]\left | A \right |\leq B\Leftrightarrow -B\leq A\leq B[/tex]