18x2 +7x -11 = 0
ax2 bx c = 0
a = 18
b = 7
c = -11
Δ = b2-4ac
Δ = 7² - (4 * 18 * -11)
Δ = 49 - (4*-198)
Δ = 49 - (-792)
Δ = 841 Δ > 0
18x2+7x-11=0
x = -b ∓ √Δ 2a
x' = -7 - √841 2*18 = -7 - 29.0 36 = -36.0 36 = -1.0
x" = -7 + √841 2*18 = -7 + 29.0 36 = 22.0 36 = 0.611111111111
x' = -324.0
x" = 198.0
S = {x ∈ R / x' = -324.0, x" = 198.0 }