5x2 -8x -4 = 0
ax2 bx c = 0
a = 5
b = -8
c = -4
Δ = b2-4ac
Δ = -8² - (4 * 5 * -4)
Δ = 64 - (4*-20)
Δ = 64 - (-80)
Δ = 144 Δ > 0
5x2-8x-4=0
x = -b ∓ √Δ 2a
x' = 8 - √144 2*5 = 8 - 12.0 10 = -4.0 10 = -0.4
x" = 8 + √144 2*5 = 8 + 12.0 10 = 20.0 10 = 2.0
x' = -10.0
x" = 50.0
S = {x ∈ R / x' = -10.0, x" = 50.0 }