5x2 -8x -13 = 0
ax2 bx c = 0
a = 5
b = -8
c = -13
Δ = b2-4ac
Δ = -8² - (4 * 5 * -13)
Δ = 64 - (4*-65)
Δ = 64 - (-260)
Δ = 324 Δ > 0
5x2-8x-13=0
x = -b ∓ √Δ 2a
x' = 8 - √324 2*5 = 8 - 18.0 10 = -10.0 10 = -1.0
x" = 8 + √324 2*5 = 8 + 18.0 10 = 26.0 10 = 2.6
x' = -25.0
x" = 65.0
S = {x ∈ R / x' = -25.0, x" = 65.0 }