-4x2 +18x -20 = 0
ax2 bx c = 0
a = -4
b = 18
c = -20
Δ = b2-4ac
Δ = 18² - (4 * -4 * -20)
Δ = 324 - (4*80)
Δ = 324 - (320)
Δ = 4 Δ > 0
-4x2+18x-20=0
x = -b ∓ √Δ 2a
x' = -18 - √4 2*-4 = -18 - 2.0 -8 = -20.0 -8 = 2.5
x" = -18 + √4 2*-4 = -18 + 2.0 -8 = -16.0 -8 = 2.0
x' = 40.0
x" = 32.0
S = {x ∈ R / x' = 40.0, x" = 32.0 }