x2 x =0

-4x2 -12x -9 = 0

ax2 bx c = 0

a = -4

b = -12

c = -9

Δ = b2-4ac

Δ = -12² - (4 * -4 * -9)

Δ = 144 - (4*36)

Δ = 144 - (144)

Δ = 0      Δ = 0

x = -b 2*a

x = 12 2*-4

x = -1.5

S = {x ∈ R / x = -1.5}