-18x2 +7x +1 = 0
ax2 bx c = 0
a = -18
b = 7
c = 1
Δ = b2-4ac
Δ = 7² - (4 * -18 * 1)
Δ = 49 - (4*-18)
Δ = 49 - (-72)
Δ = 121 Δ > 0
-18x2+7x+1=0
x = -b ∓ √Δ 2a
x' = -7 - √121 2*-18 = -7 - 11.0 -36 = -18.0 -36 = 0.5
x" = -7 + √121 2*-18 = -7 + 11.0 -36 = 4.0 -36 = -0.111111111111
x' = 162.0
x" = -36.0
S = {x ∈ R / x' = 162.0, x" = -36.0 }