-12x2 +8x +15 = 0
ax2 bx c = 0
a = -12
b = 8
c = 15
Δ = b2-4ac
Δ = 8² - (4 * -12 * 15)
Δ = 64 - (4*-180)
Δ = 64 - (-720)
Δ = 784 Δ > 0
-12x2+8x+15=0
x = -b ∓ √Δ 2a
x' = -8 - √784 2*-12 = -8 - 28.0 -24 = -36.0 -24 = 1.5
x" = -8 + √784 2*-12 = -8 + 28.0 -24 = 20.0 -24 = -0.833333333333
x' = 216.0
x" = -120.0
S = {x ∈ R / x' = 216.0, x" = -120.0 }