a) 2x/3 + (2x -1)/6 = 4 - x/3
⇔ (2.2x)/6 + (2x -1)/6 = 12/3 - x/3
⇔ (4x +2x -1)/6 = (12-x)/3
⇔ (6x -1)/6 = (12-x)/3
⇒ 3.(6x-1) = 6.(12-x)
⇔ 18x -3 = 72 -6x
⇔ 18x +6x = 72 +3
⇔ 24x = 75
⇔ x = 75 ÷ 24
⇔ x = 25/8
Vậy S= {25/8}
b) (x-1)/2 + (x-1)/4 = 1- [2.(x-1)]/3
⇔ [2.(x-1)]/4 + (x-1)/4 = 3/3 - (2x -2)/3
⇔ (2x -2 +x -1)/4 = (3-2x +2)/3
⇔ (3x -3)/4 = (5 -2x)/3
⇒ 4.(5-2x) = 3.(3x-3)
⇔ 20 -8x = 9x -9
⇔ -8x -9x = -9 -20
⇔ -17x = -29
⇔ x = -29 ÷ (-17)
⇔ x = 29/17
Vậy S= {29/17}
c) (2-x)/2001 - 1 = (1-x)/2002 - x/2003
⇔ (2-x)/2001 = (1-x)/2002 - x/2003 +1
⇔ (2-x)/2001 + 1 = (1-x)/2002 +1 - x/2003 +1
⇔ (2003-x)/2001 = (2003-x)/2002 - (2003 -x)/2003
⇔ (2003-x)/2001 - (2003-x)/2002 + (2003 -x)/2003 = 0
⇔ (2003-x).(1/2001 - 1/2002 + 1/2003) = 0
⇔ 2003 -x = 0
⇔ x = 2003
Vậy S= {2003}
