-9x2 -14x +23 = 0
ax2 bx c = 0
a = -9
b = -14
c = 23
Δ = b2-4ac
Δ = -14² - (4 * -9 * 23)
Δ = 196 - (4*-207)
Δ = 196 - (-828)
Δ = 1024 Δ > 0
-9x2-14x+23=0
x = -b ∓ √Δ 2a
x' = 14 - √1024 2*-9 = 14 - 32.0 -18 = -18.0 -18 = 1.0
x" = 14 + √1024 2*-9 = 14 + 32.0 -18 = 46.0 -18 = -2.55555555556
x' = 81.0
x" = -207.0
S = {x ∈ R / x' = 81.0, x" = -207.0 }