-9x2 +2x +11 = 0
ax2 bx c = 0
a = -9
b = 2
c = 11
Δ = b2-4ac
Δ = 2² - (4 * -9 * 11)
Δ = 4 - (4*-99)
Δ = 4 - (-396)
Δ = 400 Δ > 0
-9x2+2x+11=0
x = -b ∓ √Δ 2a
x' = -2 - √400 2*-9 = -2 - 20.0 -18 = -22.0 -18 = 1.22222222222
x" = -2 + √400 2*-9 = -2 + 20.0 -18 = 18.0 -18 = -1.0
x' = 99.0
x" = -81.0
S = {x ∈ R / x' = 99.0, x" = -81.0 }