-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 }