(3x+2)² -(3x-2)²= 5x+38
⇔ (3x +2 -3x +2).(3x +2 +3x -2) = 5x +38
⇔ 4.9x =5x +38
⇔ 36x = 5x +38
⇔ 36x -5x = 38
⇔ 31x = 38
⇔ x = 38/31
Vậy S= {38/31}
(3x-1)(x+3) = (2-x)(5-3x)
⇔ 3x² +8x -3 = 10 -11x +3x²
⇔ 3x² -3x² +8x +11x = 10 +3
⇔ 19x = 13
⇔ x = 13/19
Vậy S= {13/19}