18x2 -13x -5 = 0
ax2 bx c = 0
a = 18
b = -13
c = -5
Δ = b2-4ac
Δ = -13² - (4 * 18 * -5)
Δ = 169 - (4*-90)
Δ = 169 - (-360)
Δ = 529 Δ > 0
18x2-13x-5=0
x = -b ∓ √Δ 2a
x' = 13 - √529 2*18 = 13 - 23.0 36 = -10.0 36 = -0.277777777778
x" = 13 + √529 2*18 = 13 + 23.0 36 = 36.0 36 = 1.0
x' = -90.0
x" = 324.0
S = {x ∈ R / x' = -90.0, x" = 324.0 }