-3x2 +9x +12 = 0
ax2 bx c = 0
a = -3
b = 9
c = 12
Δ = b2-4ac
Δ = 9² - (4 * -3 * 12)
Δ = 81 - (4*-36)
Δ = 81 - (-144)
Δ = 225 Δ > 0
-3x2+9x+12=0
x = -b ∓ √Δ 2a
x' = -9 - √225 2*-3 = -9 - 15.0 -6 = -24.0 -6 = 4.0
x" = -9 + √225 2*-3 = -9 + 15.0 -6 = 6.0 -6 = -1.0
x' = 36.0
x" = -9.0
S = {x ∈ R / x' = 36.0, x" = -9.0 }