5x2 -11x -12 = 0
ax2 bx c = 0
a = 5
b = -11
c = -12
Δ = b2-4ac
Δ = -11² - (4 * 5 * -12)
Δ = 121 - (4*-60)
Δ = 121 - (-240)
Δ = 361 Δ > 0
5x2-11x-12=0
x = -b ∓ √Δ 2a
x' = 11 - √361 2*5 = 11 - 19.0 10 = -8.0 10 = -0.8
x" = 11 + √361 2*5 = 11 + 19.0 10 = 30.0 10 = 3.0
x' = -20.0
x" = 75.0
S = {x ∈ R / x' = -20.0, x" = 75.0 }