5x2 +9x +4 = 0
ax2 bx c = 0
a = 5
b = 9
c = 4
Δ = b2-4ac
Δ = 9² - (4 * 5 * 4)
Δ = 81 - (4*20)
Δ = 81 - (80)
Δ = 1 Δ > 0
5x2+9x+4=0
x = -b ∓ √Δ 2a
x' = -9 - √1 2*5 = -9 - 1.0 10 = -10.0 10 = -1.0
x" = -9 + √1 2*5 = -9 + 1.0 10 = -8.0 10 = -0.8
x' = -25.0
x" = -20.0
S = {x ∈ R / x' = -25.0, x" = -20.0 }