-1x2 -18x +19 = 0
ax2 bx c = 0
a = -1
b = -18
c = 19
Δ = b2-4ac
Δ = -18² - (4 * -1 * 19)
Δ = 324 - (4*-19)
Δ = 324 - (-76)
Δ = 400 Δ > 0
-x2-18x+19=0
x = -b ∓ √Δ 2a
x' = 18 - √400 2*-1 = 18 - 20.0 -2 = -2.0 -2 = 1.0
x" = 18 + √400 2*-1 = 18 + 20.0 -2 = 38.0 -2 = -19.0
x' = 1.0
x" = -19.0
S = {x ∈ R / x' = 1.0, x" = -19.0 }