-6x2 +21x +12 = 0
ax2 bx c = 0
a = -6
b = 21
c = 12
Δ = b2-4ac
Δ = 21² - (4 * -6 * 12)
Δ = 441 - (4*-72)
Δ = 441 - (-288)
Δ = 729 Δ > 0
-6x2+21x+12=0
x = -b ∓ √Δ 2a
x' = -21 - √729 2*-6 = -21 - 27.0 -12 = -48.0 -12 = 4.0
x" = -21 + √729 2*-6 = -21 + 27.0 -12 = 6.0 -12 = -0.5
x' = 144.0
x" = -18.0
S = {x ∈ R / x' = 144.0, x" = -18.0 }