-1x2 -9x -8 = 0
ax2 bx c = 0
a = -1
b = -9
c = -8
Δ = b2-4ac
Δ = -9² - (4 * -1 * -8)
Δ = 81 - (4*8)
Δ = 81 - (32)
Δ = 49 Δ > 0
-x2-9x-8=0
x = -b ∓ √Δ 2a
x' = 9 - √49 2*-1 = 9 - 7.0 -2 = 2.0 -2 = -1.0
x" = 9 + √49 2*-1 = 9 + 7.0 -2 = 16.0 -2 = -8.0
x' = -1.0
x" = -8.0
S = {x ∈ R / x' = -1.0, x" = -8.0 }