-9x2 +10x -1 = 0
ax2 bx c = 0
a = -9
b = 10
c = -1
Δ = b2-4ac
Δ = 10² - (4 * -9 * -1)
Δ = 100 - (4*9)
Δ = 100 - (36)
Δ = 64 Δ > 0
-9x2+10x-1=0
x = -b ∓ √Δ 2a
x' = -10 - √64 2*-9 = -10 - 8.0 -18 = -18.0 -18 = 1.0
x" = -10 + √64 2*-9 = -10 + 8.0 -18 = -2.0 -18 = 0.111111111111
x' = 81.0
x" = 9.0
S = {x ∈ R / x' = 81.0, x" = 9.0 }