Odpowiedź:
y = x² + 2x - 9
y = 2x
x² +2x -9 = 2x
x² + 2x -2x - 9 = 0
x² - 9 = 0
(x - 3)(x + 3) = 0
x - 3 = 0 ∨ x +3 = 0
x₁ = 3 ∨ x₂ = - 3
y₁ = 2x₁ = 2 * 3 = 6
y₂ = 2x₂ =2 * (- 3) = - 6
Odp: x₁ = 3 , y₁ = 6 ∨ x₂ = - 3 , y₂ = - 6
