-2x2 +3x +9 = 0
ax2 bx c = 0
a = -2
b = 3
c = 9
Δ = b2-4ac
Δ = 3² - (4 * -2 * 9)
Δ = 9 - (4*-18)
Δ = 9 - (-72)
Δ = 81 Δ > 0
-2x2+3x+9=0
x = -b ∓ √Δ 2a
x' = -3 - √81 2*-2 = -3 - 9.0 -4 = -12.0 -4 = 3.0
x" = -3 + √81 2*-2 = -3 + 9.0 -4 = 6.0 -4 = -1.5
x' = 12.0
x" = -6.0
S = {x ∈ R / x' = 12.0, x" = -6.0 }