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 = -30.0 30 = -1.0
x" = -9 + √441 2*15 = -9 + 21.0 30 = 12.0 30 = 0.4
x' = -225.0
x" = 90.0
S = {x ∈ R / x' = -225.0, x" = 90.0 }