-18x2 +9x +9 = 0
ax2 bx c = 0
a = -18
b = 9
c = 9
Δ = b2-4ac
Δ = 9² - (4 * -18 * 9)
Δ = 81 - (4*-162)
Δ = 81 - (-648)
Δ = 729 Δ > 0
-18x2+9x+9=0
x = -b ∓ √Δ 2a
x' = -9 - √729 2*-18 = -9 - 27.0 -36 = -36.0 -36 = 1.0
x" = -9 + √729 2*-18 = -9 + 27.0 -36 = 18.0 -36 = -0.5
x' = 324.0
x" = -162.0
S = {x ∈ R / x' = 324.0, x" = -162.0 }