2x² - 5x = - 3
x² - 5/2 x = - 3/2
x² - 5/2 x + 25/16 = - 3/2 + 25/16
(x - 5/4)² = 1/16
x - 5/4 = ± 1/4
x₁ = 3/2 ,x₂ = 1
-3x² - 2x +1 = 0
3x² + 2x = 1
x² + 2/3 x = 1/3
x² + 2/3 x + 1/9 = 1/3 + 1/9
(x+1/3)² = 4/9
x+ 1/3 = ± 2/3
x₁ = 1/3 ,x₂ = - 1