a)
[tex]\it |x-1|(|x+2|-3)\leq0\Rightarrow\begin{cases} \it |x-1|=0\Rightarrow x-1=0\Rightarrow x=1\ \ \ \ \ (1)\\ \\ sau\\ \\ \it|x+2|-3\leq0\ \Rightarrow |x+2|\leq3\ \ \ \ \ \ \ (2)\end{cases}\\ \\ \\ (2) \Rightarrow \ -3\leq x+2\leq3|_{-2} \Rightarrow \ \ -5\leq x\leq1 \Rightarrow \ \ x\in[-5,\ \ 1]\ \ \ \ \ \ (3)\\ \\ \\ (1),\ (3) \Rightarrow A=[-5,\ \ 1][/tex]
c)
[tex]\it |x-3|(7-|2x-11|)>0 \Rightarrow \begin{cases} \it |x-3|\ne0 \Rightarrow x-3\ne0 \Rightarrow x\ne3\ \ \ \ \ (1)\\ \\ \it 7-|2x-11|>0 \Rightarrow |2x-11|<7\ \ \ \ (2)\end{cases}\\ \\ \\ (2) \Rightarrow -7<2x-11<7|_{+11} \Rightarrow 4<2x<18|_{:2} \Rightarrow 2<x<9 \Rightarrow \\ \\ \Rightarrow x\in(2,\ 9)\ \ \ \ \ (3)\\ \\ \\ (1),\ (3)\ \Rightarrow A=(2,\ \ 9) \setminus \{3\}[/tex]
