-18x2 +2x +20 = 0
ax2 bx c = 0
a = -18
b = 2
c = 20
Δ = b2-4ac
Δ = 2² - (4 * -18 * 20)
Δ = 4 - (4*-360)
Δ = 4 - (-1440)
Δ = 1444 Δ > 0
-18x2+2x+20=0
x = -b ∓ √Δ 2a
x' = -2 - √1444 2*-18 = -2 - 38.0 -36 = -40.0 -36 = 1.11111111111
x" = -2 + √1444 2*-18 = -2 + 38.0 -36 = 36.0 -36 = -1.0
x' = 360.0
x" = -324.0
S = {x ∈ R / x' = 360.0, x" = -324.0 }