-9x2 -2x +7 = 0
ax2 bx c = 0
a = -9
b = -2
c = 7
Δ = b2-4ac
Δ = -2² - (4 * -9 * 7)
Δ = 4 - (4*-63)
Δ = 4 - (-252)
Δ = 256 Δ > 0
-9x2-2x+7=0
x = -b ∓ √Δ 2a
x' = 2 - √256 2*-9 = 2 - 16.0 -18 = -14.0 -18 = 0.777777777778
x" = 2 + √256 2*-9 = 2 + 16.0 -18 = 18.0 -18 = -1.0
x' = 63.0
x" = -81.0
S = {x ∈ R / x' = 63.0, x" = -81.0 }