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 = -18.0 36 = -0.5
x" = 9 + √729 2*18 = 9 + 27.0 36 = 36.0 36 = 1.0
x' = -162.0
x" = 324.0
S = {x ∈ R / x' = -162.0, x" = 324.0 }