15x2 -14x -8 = 0
ax2 bx c = 0
a = 15
b = -14
c = -8
Δ = b2-4ac
Δ = -14² - (4 * 15 * -8)
Δ = 196 - (4*-120)
Δ = 196 - (-480)
Δ = 676 Δ > 0
15x2-14x-8=0
x = -b ∓ √Δ 2a
x' = 14 - √676 2*15 = 14 - 26.0 30 = -12.0 30 = -0.4
x" = 14 + √676 2*15 = 14 + 26.0 30 = 40.0 30 = 1.33333333333
x' = -90.0
x" = 300.0
S = {x ∈ R / x' = -90.0, x" = 300.0 }