-12x2+12x-3=0

Δ = b2-4ac

Δ = 12² - (4 * -12 * -3)

Δ = 144 - (4*36)

Δ = 144 - (144)

Δ = 0      Δ = 0

x = -b 2*a

x = -12 2*-12

x = 0.5

S = {x ∈ R / x = 0.5}