18x2 -5x -13 = 0
ax2 bx c = 0
a = 18
b = -5
c = -13
Δ = b2-4ac
Δ = -5² - (4 * 18 * -13)
Δ = 25 - (4*-234)
Δ = 25 - (-936)
Δ = 961 Δ > 0
18x2-5x-13=0
x = -b ∓ √Δ 2a
x' = 5 - √961 2*18 = 5 - 31.0 36 = -26.0 36 = -0.722222222222
x" = 5 + √961 2*18 = 5 + 31.0 36 = 36.0 36 = 1.0
x' = -234.0
x" = 324.0
S = {x ∈ R / x' = -234.0, x" = 324.0 }