5x2 -18x +13 = 0
ax2 bx c = 0
a = 5
b = -18
c = 13
Δ = b2-4ac
Δ = -18² - (4 * 5 * 13)
Δ = 324 - (4*65)
Δ = 324 - (260)
Δ = 64 Δ > 0
5x2-18x+13=0
x = -b ∓ √Δ 2a
x' = 18 - √64 2*5 = 18 - 8.0 10 = 10.0 10 = 1.0
x" = 18 + √64 2*5 = 18 + 8.0 10 = 26.0 10 = 2.6
x' = 25.0
x" = 65.0
S = {x ∈ R / x' = 25.0, x" = 65.0 }