x2 x =0

-1x2 -6x -9 = 0

ax2 bx c = 0

a = -1

b = -6

c = -9

Δ = b2-4ac

Δ = -6² - (4 * -1 * -9)

Δ = 36 - (4*9)

Δ = 36 - (36)

Δ = 0      Δ = 0

x = -b 2*a

x = 6 2*-1

x = -3.0

S = {x ∈ R / x = -3.0}