-15x2 +13x +6 = 0
ax2 bx c = 0
a = -15
b = 13
c = 6
Δ = b2-4ac
Δ = 13² - (4 * -15 * 6)
Δ = 169 - (4*-90)
Δ = 169 - (-360)
Δ = 529 Δ > 0
-15x2+13x+6=0
x = -b ∓ √Δ 2a
x' = -13 - √529 2*-15 = -13 - 23.0 -30 = -36.0 -30 = 1.2
x" = -13 + √529 2*-15 = -13 + 23.0 -30 = 10.0 -30 = -0.333333333333
x' = 270.0
x" = -75.0
S = {x ∈ R / x' = 270.0, x" = -75.0 }