1). 6x² + x - 1 = 0
D = b² - 4ac
D = 1 - 4 × 6 × ( - 1) =1 + 24 = √25 = 5
x₁ = - 1 + 5/ 2×6= 4/12 = 1/3
x₂ = - 1 - 5/2×6 = - 6/12 = - 1/2
2) x² - 5x - 1 = 0
D = 25 - 4 × 1 × ( - 1) = 25 + 4 = 29
x₁ = 5 + √29/2
x² = 5 - √29/2
3) 2x² - 5x + 3 = 0
D = 25 - 4 × 2 × 3 = 25 - 24 = √1
x₁ = 5 + 1 / 4 = 6/4 = 3/2
x₂ = 5 - 1 / 4 = 1
4) x² + 3x + 1 = 0
D = 9 - 4 × 1 × 1 = 9 - 4 = √5
x₁ = - 3 + √5 / 2
x₂ = - 3 - √5/2
5) 3x² + 7x - 6 = 0
D = 49 - 4 × 3 × ( - 6) = 49 + 72 = 121
x₁ = - 7 + 11/ 6 = 4/6 = 2/3
x₂ = - 7 - 11 / 6 = -18/6 = - 3