5x2 +23x +18 = 0
ax2 bx c = 0
a = 5
b = 23
c = 18
Δ = b2-4ac
Δ = 23² - (4 * 5 * 18)
Δ = 529 - (4*90)
Δ = 529 - (360)
Δ = 169 Δ > 0
5x2+23x+18=0
x = -b ∓ √Δ 2a
x' = -23 - √169 2*5 = -23 - 13.0 10 = -36.0 10 = -3.6
x" = -23 + √169 2*5 = -23 + 13.0 10 = -10.0 10 = -1.0
x' = -90.0
x" = -25.0
S = {x ∈ R / x' = -90.0, x" = -25.0 }