-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 = -46.0 -18 = 2.55555555556
x" = -14 + √1024 2*-9 = -14 + 32.0 -18 = 18.0 -18 = -1.0
x' = 207.0
x" = -81.0
S = {x ∈ R / x' = 207.0, x" = -81.0 }