-12x2 +3x +9 = 0
ax2 bx c = 0
a = -12
b = 3
c = 9
Δ = b2-4ac
Δ = 3² - (4 * -12 * 9)
Δ = 9 - (4*-108)
Δ = 9 - (-432)
Δ = 441 Δ > 0
-12x2+3x+9=0
x = -b ∓ √Δ 2a
x' = -3 - √441 2*-12 = -3 - 21.0 -24 = -24.0 -24 = 1.0
x" = -3 + √441 2*-12 = -3 + 21.0 -24 = 18.0 -24 = -0.75
x' = 144.0
x" = -108.0
S = {x ∈ R / x' = 144.0, x" = -108.0 }