-4x2 +x +5 = 0
ax2 bx c = 0
a = -4
b = 1
c = 5
Δ = b2-4ac
Δ = ² - (4 * -4 * 5)
Δ = 1 - (4*-20)
Δ = 1 - (-80)
Δ = 81 Δ > 0
-4x2+x+5=0
x = -b ∓ √Δ 2a
x' = -1 - √81 2*-4 = -1 - 9.0 -8 = -10.0 -8 = 1.25
x" = -1 + √81 2*-4 = -1 + 9.0 -8 = 8.0 -8 = -1.0
x' = 20.0
x" = -16.0
S = {x ∈ R / x' = 20.0, x" = -16.0 }