15x2 +2x -1 = 0
ax2 bx c = 0
a = 15
b = 2
c = -1
Δ = b2-4ac
Δ = 2² - (4 * 15 * -1)
Δ = 4 - (4*-15)
Δ = 4 - (-60)
Δ = 64 Δ > 0
15x2+2x-1=0
x = -b ∓ √Δ 2a
x' = -2 - √64 2*15 = -2 - 8.0 30 = -10.0 30 = -0.333333333333
x" = -2 + √64 2*15 = -2 + 8.0 30 = 6.0 30 = 0.2
x' = -75.0
x" = 45.0
S = {x ∈ R / x' = -75.0, x" = 45.0 }