-9x2 -16x +4 = 0
ax2 bx c = 0
a = -9
b = -16
c = 4
Δ = b2-4ac
Δ = -16² - (4 * -9 * 4)
Δ = 256 - (4*-36)
Δ = 256 - (-144)
Δ = 400 Δ > 0
-9x2-16x+4=0
x = -b ∓ √Δ 2a
x' = 16 - √400 2*-9 = 16 - 20.0 -18 = -4.0 -18 = 0.222222222222
x" = 16 + √400 2*-9 = 16 + 20.0 -18 = 36.0 -18 = -2.0
x' = 18.0
x" = -162.0
S = {x ∈ R / x' = 18.0, x" = -162.0 }