5x2 +x -4 = 0
ax2 bx c = 0
a = 5
b = 1
c = -4
Δ = b2-4ac
Δ = ² - (4 * 5 * -4)
Δ = 1 - (4*-20)
Δ = 1 - (-80)
Δ = 81 Δ > 0
5x2+x-4=0
x = -b ∓ √Δ 2a
x' = -1 - √81 2*5 = -1 - 9.0 10 = -10.0 10 = -1.0
x" = -1 + √81 2*5 = -1 + 9.0 10 = 8.0 10 = 0.8
x' = -25.0
x" = 20.0
S = {x ∈ R / x' = -25.0, x" = 20.0 }