18x2 +x -19 = 0
ax2 bx c = 0
a = 18
b = 1
c = -19
Δ = b2-4ac
Δ = ² - (4 * 18 * -19)
Δ = 1 - (4*-342)
Δ = 1 - (-1368)
Δ = 1369 Δ > 0
18x2+x-19=0
x = -b ∓ √Δ 2a
x' = -1 - √1369 2*18 = -1 - 37.0 36 = -38.0 36 = -1.05555555556
x" = -1 + √1369 2*18 = -1 + 37.0 36 = 36.0 36 = 1.0
x' = -342.0
x" = 324.0
S = {x ∈ R / x' = -342.0, x" = 324.0 }