-1x2 -x +2 = 0
ax2 bx c = 0
a = -1
b = -1
c = 2
Δ = b2-4ac
Δ = -² - (4 * -1 * 2)
Δ = 1 - (4*-2)
Δ = 1 - (-8)
Δ = 9 Δ > 0
-x2-x+2=0
x = -b ∓ √Δ 2a
x' = 1 - √9 2*-1 = 1 - 3.0 -2 = -2.0 -2 = 1.0
x" = 1 + √9 2*-1 = 1 + 3.0 -2 = 4.0 -2 = -2.0
x' = 1.0
x" = -2.0
S = {x ∈ R / x' = 1.0, x" = -2.0 }