-4x2 +x +18 = 0
ax2 bx c = 0
a = -4
b = 1
c = 18
Δ = b2-4ac
Δ = ² - (4 * -4 * 18)
Δ = 1 - (4*-72)
Δ = 1 - (-288)
Δ = 289 Δ > 0
-4x2+x+18=0
x = -b ∓ √Δ 2a
x' = -1 - √289 2*-4 = -1 - 17.0 -8 = -18.0 -8 = 2.25
x" = -1 + √289 2*-4 = -1 + 17.0 -8 = 16.0 -8 = -2.0
x' = 36.0
x" = -32.0
S = {x ∈ R / x' = 36.0, x" = -32.0 }