5x2 -10x -15 = 0
ax2 bx c = 0
a = 5
b = -10
c = -15
Δ = b2-4ac
Δ = -10² - (4 * 5 * -15)
Δ = 100 - (4*-75)
Δ = 100 - (-300)
Δ = 400 Δ > 0
5x2-10x-15=0
x = -b ∓ √Δ 2a
x' = 10 - √400 2*5 = 10 - 20.0 10 = -10.0 10 = -1.0
x" = 10 + √400 2*5 = 10 + 20.0 10 = 30.0 10 = 3.0
x' = -25.0
x" = 75.0
S = {x ∈ R / x' = -25.0, x" = 75.0 }