-18x2 +23x -7 = 0
ax2 bx c = 0
a = -18
b = 23
c = -7
Δ = b2-4ac
Δ = 23² - (4 * -18 * -7)
Δ = 529 - (4*126)
Δ = 529 - (504)
Δ = 25 Δ > 0
-18x2+23x-7=0
x = -b ∓ √Δ 2a
x' = -23 - √25 2*-18 = -23 - 5.0 -36 = -28.0 -36 = 0.777777777778
x" = -23 + √25 2*-18 = -23 + 5.0 -36 = -18.0 -36 = 0.5
x' = 252.0
x" = 162.0
S = {x ∈ R / x' = 252.0, x" = 162.0 }