18x2 +13x -11 = 0
ax2 bx c = 0
a = 18
b = 13
c = -11
Δ = b2-4ac
Δ = 13² - (4 * 18 * -11)
Δ = 169 - (4*-198)
Δ = 169 - (-792)
Δ = 961 Δ > 0
18x2+13x-11=0
x = -b ∓ √Δ 2a
x' = -13 - √961 2*18 = -13 - 31.0 36 = -44.0 36 = -1.22222222222
x" = -13 + √961 2*18 = -13 + 31.0 36 = 18.0 36 = 0.5
x' = -396.0
x" = 162.0
S = {x ∈ R / x' = -396.0, x" = 162.0 }