-1x2 -3x +18 = 0
ax2 bx c = 0
a = -1
b = -3
c = 18
Δ = b2-4ac
Δ = -3² - (4 * -1 * 18)
Δ = 9 - (4*-18)
Δ = 9 - (-72)
Δ = 81 Δ > 0
-x2-3x+18=0
x = -b ∓ √Δ 2a
x' = 3 - √81 2*-1 = 3 - 9.0 -2 = -6.0 -2 = 3.0
x" = 3 + √81 2*-1 = 3 + 9.0 -2 = 12.0 -2 = -6.0
x' = 3.0
x" = -6.0
S = {x ∈ R / x' = 3.0, x" = -6.0 }