5x2 -13x +8 = 0
ax2 bx c = 0
a = 5
b = -13
c = 8
Δ = b2-4ac
Δ = -13² - (4 * 5 * 8)
Δ = 169 - (4*40)
Δ = 169 - (160)
Δ = 9 Δ > 0
5x2-13x+8=0
x = -b ∓ √Δ 2a
x' = 13 - √9 2*5 = 13 - 3.0 10 = 10.0 10 = 1.0
x" = 13 + √9 2*5 = 13 + 3.0 10 = 16.0 10 = 1.6
x' = 25.0
x" = 40.0
S = {x ∈ R / x' = 25.0, x" = 40.0 }