-3x2 -15x -12 = 0
ax2 bx c = 0
a = -3
b = -15
c = -12
Δ = b2-4ac
Δ = -15² - (4 * -3 * -12)
Δ = 225 - (4*36)
Δ = 225 - (144)
Δ = 81 Δ > 0
-3x2-15x-12=0
x = -b ∓ √Δ 2a
x' = 15 - √81 2*-3 = 15 - 9.0 -6 = 6.0 -6 = -1.0
x" = 15 + √81 2*-3 = 15 + 9.0 -6 = 24.0 -6 = -4.0
x' = -9.0
x" = -36.0
S = {x ∈ R / x' = -9.0, x" = -36.0 }