1/ x.(x - 3) = (x + 2)²
⇔ x² - 3x = x² + 4x + 4
⇔ x² - x² - 3x - 4x = 4
⇔ -7x = 4
⇔ x = -4/7
Vậy x = -4/7
2/ 2x.(x + 1) = (x - 1).(2x + 1)
⇔ 2x² + 2x = 2x² + x - 2x - 1
⇔ 2x² - 2x² + 2x - x + 2x = -1
⇔ 3x = -1
⇔ x = -1/3
Vậy x = -1/3
3/ x.(x + 2) + (x - 1).(x + 1) = 2x² + 7
⇔ x² + 2x + x² + x - x - 1 - 2x² = 7
⇔ 2x = 7 + 1
⇔ 2x = 8
⇔ x = 4
Vậy x = 4