-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 = -18.0 -24 = 0.75
x" = 19 + √1369 2*-12 = 19 + 37.0 -24 = 56.0 -24 = -2.33333333333
x' = 108.0
x" = -336.0
S = {x ∈ R / x' = 108.0, x" = -336.0 }