`|x-1|=2x+3` Ta có: `|x-1|=x-1` khi `x-1ge0<=>xge1` `|x-1|=-(x-1)=-x+1` khi `x-1<0<=>x<1` TH`1`:`xge1` `x-1=2x+3` `<=>x-2x=3+1` `<=>-x=4` `<=>x=-4(KTM)` TH`2`:`x<1` `x-1=-2x-3` `<=>x+2x=-3+1` `<=>x3=-2` `<=>x=-2/3(TM)` Vậy phương trình có nghiệm `S={-2/3}`
