-18x2 +17x +13 = 0
ax2 bx c = 0
a = -18
b = 17
c = 13
Δ = b2-4ac
Δ = 17² - (4 * -18 * 13)
Δ = 289 - (4*-234)
Δ = 289 - (-936)
Δ = 1225 Δ > 0
-18x2+17x+13=0
x = -b ∓ √Δ 2a
x' = -17 - √1225 2*-18 = -17 - 35.0 -36 = -52.0 -36 = 1.44444444444
x" = -17 + √1225 2*-18 = -17 + 35.0 -36 = 18.0 -36 = -0.5
x' = 468.0
x" = -162.0
S = {x ∈ R / x' = 468.0, x" = -162.0 }