-1x2 +2x +3 = 0
ax2 bx c = 0
a = -1
b = 2
c = 3
Δ = b2-4ac
Δ = 2² - (4 * -1 * 3)
Δ = 4 - (4*-3)
Δ = 4 - (-12)
Δ = 16 Δ > 0
-x2+2x+3=0
x = -b ∓ √Δ 2a
x' = -2 - √16 2*-1 = -2 - 4.0 -2 = -6.0 -2 = 3.0
x" = -2 + √16 2*-1 = -2 + 4.0 -2 = 2.0 -2 = -1.0
x' = 3.0
x" = -1.0
S = {x ∈ R / x' = 3.0, x" = -1.0 }