-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 = -30.0 -6 = 5.0
x" = -12 + √324 2*-3 = -12 + 18.0 -6 = 6.0 -6 = -1.0
x' = 45.0
x" = -9.0
S = {x ∈ R / x' = 45.0, x" = -9.0 }