18x2 -14x -4 = 0
ax2 bx c = 0
a = 18
b = -14
c = -4
Δ = b2-4ac
Δ = -14² - (4 * 18 * -4)
Δ = 196 - (4*-72)
Δ = 196 - (-288)
Δ = 484 Δ > 0
18x2-14x-4=0
x = -b ∓ √Δ 2a
x' = 14 - √484 2*18 = 14 - 22.0 36 = -8.0 36 = -0.222222222222
x" = 14 + √484 2*18 = 14 + 22.0 36 = 36.0 36 = 1.0
x' = -72.0
x" = 324.0
S = {x ∈ R / x' = -72.0, x" = 324.0 }