-12x2 -4x +21 = 0
ax2 bx c = 0
a = -12
b = -4
c = 21
Δ = b2-4ac
Δ = -4² - (4 * -12 * 21)
Δ = 16 - (4*-252)
Δ = 16 - (-1008)
Δ = 1024 Δ > 0
-12x2-4x+21=0
x = -b ∓ √Δ 2a
x' = 4 - √1024 2*-12 = 4 - 32.0 -24 = -28.0 -24 = 1.16666666667
x" = 4 + √1024 2*-12 = 4 + 32.0 -24 = 36.0 -24 = -1.5
x' = 168.0
x" = -216.0
S = {x ∈ R / x' = 168.0, x" = -216.0 }