-1x2 -4x +5 = 0
ax2 bx c = 0
a = -1
b = -4
c = 5
Δ = b2-4ac
Δ = -4² - (4 * -1 * 5)
Δ = 16 - (4*-5)
Δ = 16 - (-20)
Δ = 36 Δ > 0
-x2-4x+5=0
x = -b ∓ √Δ 2a
x' = 4 - √36 2*-1 = 4 - 6.0 -2 = -2.0 -2 = 1.0
x" = 4 + √36 2*-1 = 4 + 6.0 -2 = 10.0 -2 = -5.0
x' = 1.0
x" = -5.0
S = {x ∈ R / x' = 1.0, x" = -5.0 }