-4x2 -12x -5 = 0
ax2 bx c = 0
a = -4
b = -12
c = -5
Δ = b2-4ac
Δ = -12² - (4 * -4 * -5)
Δ = 144 - (4*20)
Δ = 144 - (80)
Δ = 64 Δ > 0
-4x2-12x-5=0
x = -b ∓ √Δ 2a
x' = 12 - √64 2*-4 = 12 - 8.0 -8 = 4.0 -8 = -0.5
x" = 12 + √64 2*-4 = 12 + 8.0 -8 = 20.0 -8 = -2.5
x' = -8.0
x" = -40.0
S = {x ∈ R / x' = -8.0, x" = -40.0 }