-4x2 -15x -11 = 0
ax2 bx c = 0
a = -4
b = -15
c = -11
Δ = b2-4ac
Δ = -15² - (4 * -4 * -11)
Δ = 225 - (4*44)
Δ = 225 - (176)
Δ = 49 Δ > 0
-4x2-15x-11=0
x = -b ∓ √Δ 2a
x' = 15 - √49 2*-4 = 15 - 7.0 -8 = 8.0 -8 = -1.0
x" = 15 + √49 2*-4 = 15 + 7.0 -8 = 22.0 -8 = -2.75
x' = -16.0
x" = -44.0
S = {x ∈ R / x' = -16.0, x" = -44.0 }