5x2 +13x -18 = 0
ax2 bx c = 0
a = 5
b = 13
c = -18
Δ = b2-4ac
Δ = 13² - (4 * 5 * -18)
Δ = 169 - (4*-90)
Δ = 169 - (-360)
Δ = 529 Δ > 0
5x2+13x-18=0
x = -b ∓ √Δ 2a
x' = -13 - √529 2*5 = -13 - 23.0 10 = -36.0 10 = -3.6
x" = -13 + √529 2*5 = -13 + 23.0 10 = 10.0 10 = 1.0
x' = -90.0
x" = 25.0
S = {x ∈ R / x' = -90.0, x" = 25.0 }