5x2 -4x -12 = 0
ax2 bx c = 0
a = 5
b = -4
c = -12
Δ = b2-4ac
Δ = -4² - (4 * 5 * -12)
Δ = 16 - (4*-60)
Δ = 16 - (-240)
Δ = 256 Δ > 0
5x2-4x-12=0
x = -b ∓ √Δ 2a
x' = 4 - √256 2*5 = 4 - 16.0 10 = -12.0 10 = -1.2
x" = 4 + √256 2*5 = 4 + 16.0 10 = 20.0 10 = 2.0
x' = -30.0
x" = 50.0
S = {x ∈ R / x' = -30.0, x" = 50.0 }