a/ Th1: Nếu x<\(\dfrac{-1}{2}\) ta có
1-x-2x-1=-3x
<=> 0=0
Th2: Nếu \(\dfrac{-1}{2}\)\(\le\)x<0 ta có
1-x+2x+1=-3x
<=> x=\(\dfrac{-1}{2}\)(t/m)
Th3 Nếu 0\(\le\)x<1 ta có
1-x+2x+1=3x
<=> x=1(kt/m)
Th4: Nếu x\(\ge\)1 ta có
x-1+2x+1=3x
<=> 0=0
Vậy..................