-12x2 +19x +21 = 0
ax2 bx c = 0
a = -12
b = 19
c = 21
Δ = b2-4ac
Δ = 19² - (4 * -12 * 21)
Δ = 361 - (4*-252)
Δ = 361 - (-1008)
Δ = 1369 Δ > 0
-12x2+19x+21=0
x = -b ∓ √Δ 2a
x' = -19 - √1369 2*-12 = -19 - 37.0 -24 = -56.0 -24 = 2.33333333333
x" = -19 + √1369 2*-12 = -19 + 37.0 -24 = 18.0 -24 = -0.75
x' = 336.0
x" = -108.0
S = {x ∈ R / x' = 336.0, x" = -108.0 }