18x2 +13x -5 = 0
ax2 bx c = 0
a = 18
b = 13
c = -5
Δ = b2-4ac
Δ = 13² - (4 * 18 * -5)
Δ = 169 - (4*-90)
Δ = 169 - (-360)
Δ = 529 Δ > 0
18x2+13x-5=0
x = -b ∓ √Δ 2a
x' = -13 - √529 2*18 = -13 - 23.0 36 = -36.0 36 = -1.0
x" = -13 + √529 2*18 = -13 + 23.0 36 = 10.0 36 = 0.277777777778
x' = -324.0
x" = 90.0
S = {x ∈ R / x' = -324.0, x" = 90.0 }