-9x2 -5x +4 = 0
ax2 bx c = 0
a = -9
b = -5
c = 4
Δ = b2-4ac
Δ = -5² - (4 * -9 * 4)
Δ = 25 - (4*-36)
Δ = 25 - (-144)
Δ = 169 Δ > 0
-9x2-5x+4=0
x = -b ∓ √Δ 2a
x' = 5 - √169 2*-9 = 5 - 13.0 -18 = -8.0 -18 = 0.444444444444
x" = 5 + √169 2*-9 = 5 + 13.0 -18 = 18.0 -18 = -1.0
x' = 36.0
x" = -81.0
S = {x ∈ R / x' = 36.0, x" = -81.0 }