-18x2 +7x +11 = 0
ax2 bx c = 0
a = -18
b = 7
c = 11
Δ = b2-4ac
Δ = 7² - (4 * -18 * 11)
Δ = 49 - (4*-198)
Δ = 49 - (-792)
Δ = 841 Δ > 0
-18x2+7x+11=0
x = -b ∓ √Δ 2a
x' = -7 - √841 2*-18 = -7 - 29.0 -36 = -36.0 -36 = 1.0
x" = -7 + √841 2*-18 = -7 + 29.0 -36 = 22.0 -36 = -0.611111111111
x' = 324.0
x" = -198.0
S = {x ∈ R / x' = 324.0, x" = -198.0 }