15x2 +x -2 = 0
ax2 bx c = 0
a = 15
b = 1
c = -2
Δ = b2-4ac
Δ = ² - (4 * 15 * -2)
Δ = 1 - (4*-30)
Δ = 1 - (-120)
Δ = 121 Δ > 0
15x2+x-2=0
x = -b ∓ √Δ 2a
x' = -1 - √121 2*15 = -1 - 11.0 30 = -12.0 30 = -0.4
x" = -1 + √121 2*15 = -1 + 11.0 30 = 10.0 30 = 0.333333333333
x' = -90.0
x" = 75.0
S = {x ∈ R / x' = -90.0, x" = 75.0 }