5x2 -12x -9 = 0
ax2 bx c = 0
a = 5
b = -12
c = -9
Δ = b2-4ac
Δ = -12² - (4 * 5 * -9)
Δ = 144 - (4*-45)
Δ = 144 - (-180)
Δ = 324 Δ > 0
5x2-12x-9=0
x = -b ∓ √Δ 2a
x' = 12 - √324 2*5 = 12 - 18.0 10 = -6.0 10 = -0.6
x" = 12 + √324 2*5 = 12 + 18.0 10 = 30.0 10 = 3.0
x' = -15.0
x" = 75.0
S = {x ∈ R / x' = -15.0, x" = 75.0 }