-6x2 +21x -9 = 0
ax2 bx c = 0
a = -6
b = 21
c = -9
Δ = b2-4ac
Δ = 21² - (4 * -6 * -9)
Δ = 441 - (4*54)
Δ = 441 - (216)
Δ = 225 Δ > 0
-6x2+21x-9=0
x = -b ∓ √Δ 2a
x' = -21 - √225 2*-6 = -21 - 15.0 -12 = -36.0 -12 = 3.0
x" = -21 + √225 2*-6 = -21 + 15.0 -12 = -6.0 -12 = 0.5
x' = 108.0
x" = 18.0
S = {x ∈ R / x' = 108.0, x" = 18.0 }