-3x2 -19x -20 = 0
ax2 bx c = 0
a = -3
b = -19
c = -20
Δ = b2-4ac
Δ = -19² - (4 * -3 * -20)
Δ = 361 - (4*60)
Δ = 361 - (240)
Δ = 121 Δ > 0
-3x2-19x-20=0
x = -b ∓ √Δ 2a
x' = 19 - √121 2*-3 = 19 - 11.0 -6 = 8.0 -6 = -1.33333333333
x" = 19 + √121 2*-3 = 19 + 11.0 -6 = 30.0 -6 = -5.0
x' = -12.0
x" = -45.0
S = {x ∈ R / x' = -12.0, x" = -45.0 }