3 x² - 6 x + 2 = 0
Δ = ( - 6 )² - 4 × 3 × 2
Δ = 36 - 24
Δ = 12
x ₁= ( 6 + 2√3 ) / 6 = 2 ( 3 + √3 ) / 6 = ( 3 + √3 ) / 3
x₂ = ( 6 - 2√3) / 6 = ( 3 - √3) / 3
