5x2 -9x +4 = 0
ax2 bx c = 0
a = 5
b = -9
c = 4
Δ = b2-4ac
Δ = -9² - (4 * 5 * 4)
Δ = 81 - (4*20)
Δ = 81 - (80)
Δ = 1 Δ > 0
5x2-9x+4=0
x = -b ∓ √Δ 2a
x' = 9 - √1 2*5 = 9 - 1.0 10 = 8.0 10 = 0.8
x" = 9 + √1 2*5 = 9 + 1.0 10 = 10.0 10 = 1.0
x' = 20.0
x" = 25.0
S = {x ∈ R / x' = 20.0, x" = 25.0 }