5x2 +4x -1 = 0
ax2 bx c = 0
a = 5
b = 4
c = -1
Δ = b2-4ac
Δ = 4² - (4 * 5 * -1)
Δ = 16 - (4*-5)
Δ = 16 - (-20)
Δ = 36 Δ > 0
5x2+4x-1=0
x = -b ∓ √Δ 2a
x' = -4 - √36 2*5 = -4 - 6.0 10 = -10.0 10 = -1.0
x" = -4 + √36 2*5 = -4 + 6.0 10 = 2.0 10 = 0.2
x' = -25.0
x" = 5.0
S = {x ∈ R / x' = -25.0, x" = 5.0 }