18x2 +x -5 = 0
ax2 bx c = 0
a = 18
b = 1
c = -5
Δ = b2-4ac
Δ = ² - (4 * 18 * -5)
Δ = 1 - (4*-90)
Δ = 1 - (-360)
Δ = 361 Δ > 0
18x2+x-5=0
x = -b ∓ √Δ 2a
x' = -1 - √361 2*18 = -1 - 19.0 36 = -20.0 36 = -0.555555555556
x" = -1 + √361 2*18 = -1 + 19.0 36 = 18.0 36 = 0.5
x' = -180.0
x" = 162.0
S = {x ∈ R / x' = -180.0, x" = 162.0 }