-18x2 -11x +7 = 0
ax2 bx c = 0
a = -18
b = -11
c = 7
Δ = b2-4ac
Δ = -11² - (4 * -18 * 7)
Δ = 121 - (4*-126)
Δ = 121 - (-504)
Δ = 625 Δ > 0
-18x2-11x+7=0
x = -b ∓ √Δ 2a
x' = 11 - √625 2*-18 = 11 - 25.0 -36 = -14.0 -36 = 0.388888888889
x" = 11 + √625 2*-18 = 11 + 25.0 -36 = 36.0 -36 = -1.0
x' = 126.0
x" = -324.0
S = {x ∈ R / x' = 126.0, x" = -324.0 }