-1x2 -8x -7 = 0
ax2 bx c = 0
a = -1
b = -8
c = -7
Δ = b2-4ac
Δ = -8² - (4 * -1 * -7)
Δ = 64 - (4*7)
Δ = 64 - (28)
Δ = 36 Δ > 0
-x2-8x-7=0
x = -b ∓ √Δ 2a
x' = 8 - √36 2*-1 = 8 - 6.0 -2 = 2.0 -2 = -1.0
x" = 8 + √36 2*-1 = 8 + 6.0 -2 = 14.0 -2 = -7.0
x' = -1.0
x" = -7.0
S = {x ∈ R / x' = -1.0, x" = -7.0 }