5x2 +18x -8 = 0
ax2 bx c = 0
a = 5
b = 18
c = -8
Δ = b2-4ac
Δ = 18² - (4 * 5 * -8)
Δ = 324 - (4*-40)
Δ = 324 - (-160)
Δ = 484 Δ > 0
5x2+18x-8=0
x = -b ∓ √Δ 2a
x' = -18 - √484 2*5 = -18 - 22.0 10 = -40.0 10 = -4.0
x" = -18 + √484 2*5 = -18 + 22.0 10 = 4.0 10 = 0.4
x' = -100.0
x" = 10.0
S = {x ∈ R / x' = -100.0, x" = 10.0 }