-4x2 -11x -7 = 0
ax2 bx c = 0
a = -4
b = -11
c = -7
Δ = b2-4ac
Δ = -11² - (4 * -4 * -7)
Δ = 121 - (4*28)
Δ = 121 - (112)
Δ = 9 Δ > 0
-4x2-11x-7=0
x = -b ∓ √Δ 2a
x' = 11 - √9 2*-4 = 11 - 3.0 -8 = 8.0 -8 = -1.0
x" = 11 + √9 2*-4 = 11 + 3.0 -8 = 14.0 -8 = -1.75
x' = -16.0
x" = -28.0
S = {x ∈ R / x' = -16.0, x" = -28.0 }