y = ½ x² - x - 2
y = x + 4
y = ax + b
½x² - x - 2 = x + 4
½x² - x - x - 2 - 4 = 0
½x² - 2x - 6 = 0 |•2
x² - 4x - 12 = 0
a = 1, b = -4, c = -12
Δ = b² - 4ac
Δ = (-4)² - 4•1•(-12) = 16 + 48 = 64
√Δ = √64 = 8
x₁ = (-b-√Δ)/2a = -(-4) - 8/2•1 = (4-8)/2 = -4/2 = -2
x₂ = (-b+√Δ)/2a = -(-4) + 8/2•1 = (4+8)/2 = 12/2 = 6
y = x + 4
y₁ = -2 + 4 = 2
y₂ = 6 + 4 = 10
A = (-2;2) i B = (6;10)
