-15x2 +8x +12 = 0
ax2 bx c = 0
a = -15
b = 8
c = 12
Δ = b2-4ac
Δ = 8² - (4 * -15 * 12)
Δ = 64 - (4*-180)
Δ = 64 - (-720)
Δ = 784 Δ > 0
-15x2+8x+12=0
x = -b ∓ √Δ 2a
x' = -8 - √784 2*-15 = -8 - 28.0 -30 = -36.0 -30 = 1.2
x" = -8 + √784 2*-15 = -8 + 28.0 -30 = 20.0 -30 = -0.666666666667
x' = 270.0
x" = -150.0
S = {x ∈ R / x' = 270.0, x" = -150.0 }