-3x2 -18x -15 = 0
ax2 bx c = 0
a = -3
b = -18
c = -15
Δ = b2-4ac
Δ = -18² - (4 * -3 * -15)
Δ = 324 - (4*45)
Δ = 324 - (180)
Δ = 144 Δ > 0
-3x2-18x-15=0
x = -b ∓ √Δ 2a
x' = 18 - √144 2*-3 = 18 - 12.0 -6 = 6.0 -6 = -1.0
x" = 18 + √144 2*-3 = 18 + 12.0 -6 = 30.0 -6 = -5.0
x' = -9.0
x" = -45.0
S = {x ∈ R / x' = -9.0, x" = -45.0 }