-4x2 -8x +5 = 0
ax2 bx c = 0
a = -4
b = -8
c = 5
Δ = b2-4ac
Δ = -8² - (4 * -4 * 5)
Δ = 64 - (4*-20)
Δ = 64 - (-80)
Δ = 144 Δ > 0
-4x2-8x+5=0
x = -b ∓ √Δ 2a
x' = 8 - √144 2*-4 = 8 - 12.0 -8 = -4.0 -8 = 0.5
x" = 8 + √144 2*-4 = 8 + 12.0 -8 = 20.0 -8 = -2.5
x' = 8.0
x" = -40.0
S = {x ∈ R / x' = 8.0, x" = -40.0 }