-9x2 -4x +5 = 0
ax2 bx c = 0
a = -9
b = -4
c = 5
Δ = b2-4ac
Δ = -4² - (4 * -9 * 5)
Δ = 16 - (4*-45)
Δ = 16 - (-180)
Δ = 196 Δ > 0
-9x2-4x+5=0
x = -b ∓ √Δ 2a
x' = 4 - √196 2*-9 = 4 - 14.0 -18 = -10.0 -18 = 0.555555555556
x" = 4 + √196 2*-9 = 4 + 14.0 -18 = 18.0 -18 = -1.0
x' = 45.0
x" = -81.0
S = {x ∈ R / x' = 45.0, x" = -81.0 }