5x2 +18x +13 = 0
ax2 bx c = 0
a = 5
b = 18
c = 13
Δ = b2-4ac
Δ = 18² - (4 * 5 * 13)
Δ = 324 - (4*65)
Δ = 324 - (260)
Δ = 64 Δ > 0
5x2+18x+13=0
x = -b ∓ √Δ 2a
x' = -18 - √64 2*5 = -18 - 8.0 10 = -26.0 10 = -2.6
x" = -18 + √64 2*5 = -18 + 8.0 10 = -10.0 10 = -1.0
x' = -65.0
x" = -25.0
S = {x ∈ R / x' = -65.0, x" = -25.0 }