-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 = -36.0 -18 = 2.0
x" = -16 + √400 2*-9 = -16 + 20.0 -18 = 4.0 -18 = -0.222222222222
x' = 162.0
x" = -18.0
S = {x ∈ R / x' = 162.0, x" = -18.0 }