-15x2 +2x +8 = 0
ax2 bx c = 0
a = -15
b = 2
c = 8
Δ = b2-4ac
Δ = 2² - (4 * -15 * 8)
Δ = 4 - (4*-120)
Δ = 4 - (-480)
Δ = 484 Δ > 0
-15x2+2x+8=0
x = -b ∓ √Δ 2a
x' = -2 - √484 2*-15 = -2 - 22.0 -30 = -24.0 -30 = 0.8
x" = -2 + √484 2*-15 = -2 + 22.0 -30 = 20.0 -30 = -0.666666666667
x' = 180.0
x" = -150.0
S = {x ∈ R / x' = 180.0, x" = -150.0 }