5x2 -2x -7 = 0
ax2 bx c = 0
a = 5
b = -2
c = -7
Δ = b2-4ac
Δ = -2² - (4 * 5 * -7)
Δ = 4 - (4*-35)
Δ = 4 - (-140)
Δ = 144 Δ > 0
5x2-2x-7=0
x = -b ∓ √Δ 2a
x' = 2 - √144 2*5 = 2 - 12.0 10 = -10.0 10 = -1.0
x" = 2 + √144 2*5 = 2 + 12.0 10 = 14.0 10 = 1.4
x' = -25.0
x" = 35.0
S = {x ∈ R / x' = -25.0, x" = 35.0 }