-1x2 -19x -18 = 0
ax2 bx c = 0
a = -1
b = -19
c = -18
Δ = b2-4ac
Δ = -19² - (4 * -1 * -18)
Δ = 361 - (4*18)
Δ = 361 - (72)
Δ = 289 Δ > 0
-x2-19x-18=0
x = -b ∓ √Δ 2a
x' = 19 - √289 2*-1 = 19 - 17.0 -2 = 2.0 -2 = -1.0
x" = 19 + √289 2*-1 = 19 + 17.0 -2 = 36.0 -2 = -18.0
x' = -1.0
x" = -18.0
S = {x ∈ R / x' = -1.0, x" = -18.0 }