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 = -40.0 30 = -1.33333333333
x" = -14 + √676 2*15 = -14 + 26.0 30 = 12.0 30 = 0.4
x' = -300.0
x" = 90.0
S = {x ∈ R / x' = -300.0, x" = 90.0 }