-4x2 +16x +20 = 0
ax2 bx c = 0
a = -4
b = 16
c = 20
Δ = b2-4ac
Δ = 16² - (4 * -4 * 20)
Δ = 256 - (4*-80)
Δ = 256 - (-320)
Δ = 576 Δ > 0
-4x2+16x+20=0
x = -b ∓ √Δ 2a
x' = -16 - √576 2*-4 = -16 - 24.0 -8 = -40.0 -8 = 5.0
x" = -16 + √576 2*-4 = -16 + 24.0 -8 = 8.0 -8 = -1.0
x' = 80.0
x" = -16.0
S = {x ∈ R / x' = 80.0, x" = -16.0 }