5x2 +x -18 = 0
ax2 bx c = 0
a = 5
b = 1
c = -18
Δ = b2-4ac
Δ = ² - (4 * 5 * -18)
Δ = 1 - (4*-90)
Δ = 1 - (-360)
Δ = 361 Δ > 0
5x2+x-18=0
x = -b ∓ √Δ 2a
x' = -1 - √361 2*5 = -1 - 19.0 10 = -20.0 10 = -2.0
x" = -1 + √361 2*5 = -1 + 19.0 10 = 18.0 10 = 1.8
x' = -50.0
x" = 45.0
S = {x ∈ R / x' = -50.0, x" = 45.0 }