-9x2 +3x +12 = 0
ax2 bx c = 0
a = -9
b = 3
c = 12
Δ = b2-4ac
Δ = 3² - (4 * -9 * 12)
Δ = 9 - (4*-108)
Δ = 9 - (-432)
Δ = 441 Δ > 0
-9x2+3x+12=0
x = -b ∓ √Δ 2a
x' = -3 - √441 2*-9 = -3 - 21.0 -18 = -24.0 -18 = 1.33333333333
x" = -3 + √441 2*-9 = -3 + 21.0 -18 = 18.0 -18 = -1.0
x' = 108.0
x" = -81.0
S = {x ∈ R / x' = 108.0, x" = -81.0 }