-15x2 -9x +6 = 0
ax2 bx c = 0
a = -15
b = -9
c = 6
Δ = b2-4ac
Δ = -9² - (4 * -15 * 6)
Δ = 81 - (4*-90)
Δ = 81 - (-360)
Δ = 441 Δ > 0
-15x2-9x+6=0
x = -b ∓ √Δ 2a
x' = 9 - √441 2*-15 = 9 - 21.0 -30 = -12.0 -30 = 0.4
x" = 9 + √441 2*-15 = 9 + 21.0 -30 = 30.0 -30 = -1.0
x' = 90.0
x" = -225.0
S = {x ∈ R / x' = 90.0, x" = -225.0 }