-18x2 +23x -5 = 0
ax2 bx c = 0
a = -18
b = 23
c = -5
Δ = b2-4ac
Δ = 23² - (4 * -18 * -5)
Δ = 529 - (4*90)
Δ = 529 - (360)
Δ = 169 Δ > 0
-18x2+23x-5=0
x = -b ∓ √Δ 2a
x' = -23 - √169 2*-18 = -23 - 13.0 -36 = -36.0 -36 = 1.0
x" = -23 + √169 2*-18 = -23 + 13.0 -36 = -10.0 -36 = 0.277777777778
x' = 324.0
x" = 90.0
S = {x ∈ R / x' = 324.0, x" = 90.0 }