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 = -18.0 36 = -0.5
x" = 17 + √1225 2*18 = 17 + 35.0 36 = 52.0 36 = 1.44444444444
x' = -162.0
x" = 468.0
S = {x ∈ R / x' = -162.0, x" = 468.0 }