-4x2 -20x +11 = 0
ax2 bx c = 0
a = -4
b = -20
c = 11
Δ = b2-4ac
Δ = -20² - (4 * -4 * 11)
Δ = 400 - (4*-44)
Δ = 400 - (-176)
Δ = 576 Δ > 0
-4x2-20x+11=0
x = -b ∓ √Δ 2a
x' = 20 - √576 2*-4 = 20 - 24.0 -8 = -4.0 -8 = 0.5
x" = 20 + √576 2*-4 = 20 + 24.0 -8 = 44.0 -8 = -5.5
x' = 8.0
x" = -88.0
S = {x ∈ R / x' = 8.0, x" = -88.0 }