-4x2 -9x -5 = 0
ax2 bx c = 0
a = -4
b = -9
c = -5
Δ = b2-4ac
Δ = -9² - (4 * -4 * -5)
Δ = 81 - (4*20)
Δ = 81 - (80)
Δ = 1 Δ > 0
-4x2-9x-5=0
x = -b ∓ √Δ 2a
x' = 9 - √1 2*-4 = 9 - 1.0 -8 = 8.0 -8 = -1.0
x" = 9 + √1 2*-4 = 9 + 1.0 -8 = 10.0 -8 = -1.25
x' = -16.0
x" = -20.0
S = {x ∈ R / x' = -16.0, x" = -20.0 }