-18x2 -13x -2 = 0
ax2 bx c = 0
a = -18
b = -13
c = -2
Δ = b2-4ac
Δ = -13² - (4 * -18 * -2)
Δ = 169 - (4*36)
Δ = 169 - (144)
Δ = 25 Δ > 0
-18x2-13x-2=0
x = -b ∓ √Δ 2a
x' = 13 - √25 2*-18 = 13 - 5.0 -36 = 8.0 -36 = -0.222222222222
x" = 13 + √25 2*-18 = 13 + 5.0 -36 = 18.0 -36 = -0.5
x' = -72.0
x" = -162.0
S = {x ∈ R / x' = -72.0, x" = -162.0 }