-4x2 -13x -9 = 0
ax2 bx c = 0
a = -4
b = -13
c = -9
Δ = b2-4ac
Δ = -13² - (4 * -4 * -9)
Δ = 169 - (4*36)
Δ = 169 - (144)
Δ = 25 Δ > 0
-4x2-13x-9=0
x = -b ∓ √Δ 2a
x' = 13 - √25 2*-4 = 13 - 5.0 -8 = 8.0 -8 = -1.0
x" = 13 + √25 2*-4 = 13 + 5.0 -8 = 18.0 -8 = -2.25
x' = -16.0
x" = -36.0
S = {x ∈ R / x' = -16.0, x" = -36.0 }