-9x2 +22x -13 = 0
ax2 bx c = 0
a = -9
b = 22
c = -13
Δ = b2-4ac
Δ = 22² - (4 * -9 * -13)
Δ = 484 - (4*117)
Δ = 484 - (468)
Δ = 16 Δ > 0
-9x2+22x-13=0
x = -b ∓ √Δ 2a
x' = -22 - √16 2*-9 = -22 - 4.0 -18 = -26.0 -18 = 1.44444444444
x" = -22 + √16 2*-9 = -22 + 4.0 -18 = -18.0 -18 = 1.0
x' = 117.0
x" = 81.0
S = {x ∈ R / x' = 117.0, x" = 81.0 }