-4x2 -16x +9 = 0
ax2 bx c = 0
a = -4
b = -16
c = 9
Δ = b2-4ac
Δ = -16² - (4 * -4 * 9)
Δ = 256 - (4*-36)
Δ = 256 - (-144)
Δ = 400 Δ > 0
-4x2-16x+9=0
x = -b ∓ √Δ 2a
x' = 16 - √400 2*-4 = 16 - 20.0 -8 = -4.0 -8 = 0.5
x" = 16 + √400 2*-4 = 16 + 20.0 -8 = 36.0 -8 = -4.5
x' = 8.0
x" = -72.0
S = {x ∈ R / x' = 8.0, x" = -72.0 }