-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 }