lập bảng biến thiên và vẽ đồ thị hàm số: a, y= |x- 1| b, y= -2x+3

$$\eqalign{ & a)\,\,y = \left| {x - 1} \right| = \left[ \matrix{ x - 1\,\,khi\,\,x \ge 1 \hfill \cr 1 - x\,\,khi\,\,x < 1 \hfill \cr} \right. \cr & y = x - 1\,\,\left( {{d_1}} \right) \cr & Cho\,\,x = 1 \Rightarrow y = 0 \Rightarrow \left( {1;0} \right) \cr & Cho\,\,x = 2 \Rightarrow y = 1 \Rightarrow \left( {2;1} \right) \cr & y = 1 - x\,\,\left( {{d_2}} \right) \cr & Cho\,\,\,x = - 1 \Rightarrow y = 2 \Rightarrow \left( { - 1;2} \right) \cr & Cho\,\,x = - 2 \Rightarrow y = 3 \Rightarrow \left( { - 2;3} \right) \cr & b)\,\,b = - 2x + 3 \cr & Cho\,\,x = 0 \Rightarrow y = 3 \Rightarrow \left( {0;3} \right) \cr & Cho\,\,x = 1 \Rightarrow y = 1 \Rightarrow \left( {1;1} \right) \cr} $$