-3x2 -12x +15 = 0
ax2 bx c = 0
a = -3
b = -12
c = 15
Δ = b2-4ac
Δ = -12² - (4 * -3 * 15)
Δ = 144 - (4*-45)
Δ = 144 - (-180)
Δ = 324 Δ > 0
-3x2-12x+15=0
x = -b ∓ √Δ 2a
x' = 12 - √324 2*-3 = 12 - 18.0 -6 = -6.0 -6 = 1.0
x" = 12 + √324 2*-3 = 12 + 18.0 -6 = 30.0 -6 = -5.0
x' = 9.0
x" = -45.0
S = {x ∈ R / x' = 9.0, x" = -45.0 }