-1x2 +x +12 = 0
ax2 bx c = 0
a = -1
b = 1
c = 12
Δ = b2-4ac
Δ = ² - (4 * -1 * 12)
Δ = 1 - (4*-12)
Δ = 1 - (-48)
Δ = 49 Δ > 0
-x2+x+12=0
x = -b ∓ √Δ 2a
x' = -1 - √49 2*-1 = -1 - 7.0 -2 = -8.0 -2 = 4.0
x" = -1 + √49 2*-1 = -1 + 7.0 -2 = 6.0 -2 = -3.0
x' = 4.0
x" = -3.0
S = {x ∈ R / x' = 4.0, x" = -3.0 }