Odpowiedź:
1.
y = 2x² + x - 1
2x² + x - 1 = 0
a = 2 , b = 1 , c = - 1
Δ = b² - 4ac = 1² - 4 * 2 * (- 1) = 1 + 8 = 9
√Δ = √9 = 3
x₁ = ( - b - √Δ)/2a = (- 1 - 3)/4 = - 4/4 = - 1
x₂ = ( - b + √Δ)/2a = (- 1 + 3)/4 = 2/4 = 1/2
x₀ = { - 1 , 1/2 }
2.
y = 3x² - 9x
3x² - 9x = 0
3x(x - 3) = 0
3x = 0 ∨ x - 3 = 0
x = 0 ∨ x = 3
x₀ = { 0 , 3 }
3.
y = - x² + 5x + 6
- x² + 5x + 6 = 0
a = - 1 , b = 5 , c = 6
Δ = b² - 4ac = 5² - 4 * (- 1) * 6 = 25 + 24 = 49
√Δ = √49 = 7
x₁ = ( - b - √Δ)/2a = (- 5 - 7)/(- 2) = - 12/(- 2) = 12/2 = 6
x₂ = ( - b + √Δ)/2a = (- 5 + 7)/(- 2) = 2/(- 2) = - 2/2 = - 1
x₀ = { - 1 , 6 }