-9x2 +19x -10 = 0
ax2 bx c = 0
a = -9
b = 19
c = -10
Δ = b2-4ac
Δ = 19² - (4 * -9 * -10)
Δ = 361 - (4*90)
Δ = 361 - (360)
Δ = 1 Δ > 0
-9x2+19x-10=0
x = -b ∓ √Δ 2a
x' = -19 - √1 2*-9 = -19 - 1.0 -18 = -20.0 -18 = 1.11111111111
x" = -19 + √1 2*-9 = -19 + 1.0 -18 = -18.0 -18 = 1.0
x' = 90.0
x" = 81.0
S = {x ∈ R / x' = 90.0, x" = 81.0 }