18x2 -15x -12 = 0
ax2 bx c = 0
a = 18
b = -15
c = -12
Δ = b2-4ac
Δ = -15² - (4 * 18 * -12)
Δ = 225 - (4*-216)
Δ = 225 - (-864)
Δ = 1089 Δ > 0
18x2-15x-12=0
x = -b ∓ √Δ 2a
x' = 15 - √1089 2*18 = 15 - 33.0 36 = -18.0 36 = -0.5
x" = 15 + √1089 2*18 = 15 + 33.0 36 = 48.0 36 = 1.33333333333
x' = -162.0
x" = 432.0
S = {x ∈ R / x' = -162.0, x" = 432.0 }