-18x2 -7x +8 = 0
ax2 bx c = 0
a = -18
b = -7
c = 8
Δ = b2-4ac
Δ = -7² - (4 * -18 * 8)
Δ = 49 - (4*-144)
Δ = 49 - (-576)
Δ = 625 Δ > 0
-18x2-7x+8=0
x = -b ∓ √Δ 2a
x' = 7 - √625 2*-18 = 7 - 25.0 -36 = -18.0 -36 = 0.5
x" = 7 + √625 2*-18 = 7 + 25.0 -36 = 32.0 -36 = -0.888888888889
x' = 162.0
x" = -288.0
S = {x ∈ R / x' = 162.0, x" = -288.0 }