15x2 -7x -8 = 0
ax2 bx c = 0
a = 15
b = -7
c = -8
Δ = b2-4ac
Δ = -7² - (4 * 15 * -8)
Δ = 49 - (4*-120)
Δ = 49 - (-480)
Δ = 529 Δ > 0
15x2-7x-8=0
x = -b ∓ √Δ 2a
x' = 7 - √529 2*15 = 7 - 23.0 30 = -16.0 30 = -0.533333333333
x" = 7 + √529 2*15 = 7 + 23.0 30 = 30.0 30 = 1.0
x' = -120.0
x" = 225.0
S = {x ∈ R / x' = -120.0, x" = 225.0 }