5x2 -6x -8 = 0
ax2 bx c = 0
a = 5
b = -6
c = -8
Δ = b2-4ac
Δ = -6² - (4 * 5 * -8)
Δ = 36 - (4*-40)
Δ = 36 - (-160)
Δ = 196 Δ > 0
5x2-6x-8=0
x = -b ∓ √Δ 2a
x' = 6 - √196 2*5 = 6 - 14.0 10 = -8.0 10 = -0.8
x" = 6 + √196 2*5 = 6 + 14.0 10 = 20.0 10 = 2.0
x' = -20.0
x" = 50.0
S = {x ∈ R / x' = -20.0, x" = 50.0 }