5x2 +18x +9 = 0
ax2 bx c = 0
a = 5
b = 18
c = 9
Δ = b2-4ac
Δ = 18² - (4 * 5 * 9)
Δ = 324 - (4*45)
Δ = 324 - (180)
Δ = 144 Δ > 0
5x2+18x+9=0
x = -b ∓ √Δ 2a
x' = -18 - √144 2*5 = -18 - 12.0 10 = -30.0 10 = -3.0
x" = -18 + √144 2*5 = -18 + 12.0 10 = -6.0 10 = -0.6
x' = -75.0
x" = -15.0
S = {x ∈ R / x' = -75.0, x" = -15.0 }