-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 }