-11x2 +8x +19 = 0
ax2 bx c = 0
a = -11
b = 8
c = 19
Δ = b2-4ac
Δ = 8² - (4 * -11 * 19)
Δ = 64 - (4*-209)
Δ = 64 - (-836)
Δ = 900 Δ > 0
-11x2+8x+19=0
x = -b ∓ √Δ 2a
x' = -8 - √900 2*-11 = -8 - 30.0 -22 = -38.0 -22 = 1.72727272727
x" = -8 + √900 2*-11 = -8 + 30.0 -22 = 22.0 -22 = -1.0
x' = 209.0
x" = -121.0
S = {x ∈ R / x' = 209.0, x" = -121.0 }