-9x2 +20x -4 = 0
ax2 bx c = 0
a = -9
b = 20
c = -4
Δ = b2-4ac
Δ = 20² - (4 * -9 * -4)
Δ = 400 - (4*36)
Δ = 400 - (144)
Δ = 256 Δ > 0
-9x2+20x-4=0
x = -b ∓ √Δ 2a
x' = -20 - √256 2*-9 = -20 - 16.0 -18 = -36.0 -18 = 2.0
x" = -20 + √256 2*-9 = -20 + 16.0 -18 = -4.0 -18 = 0.222222222222
x' = 162.0
x" = 18.0
S = {x ∈ R / x' = 162.0, x" = 18.0 }