-9x2 +8x +17 = 0
ax2 bx c = 0
a = -9
b = 8
c = 17
Δ = b2-4ac
Δ = 8² - (4 * -9 * 17)
Δ = 64 - (4*-153)
Δ = 64 - (-612)
Δ = 676 Δ > 0
-9x2+8x+17=0
x = -b ∓ √Δ 2a
x' = -8 - √676 2*-9 = -8 - 26.0 -18 = -34.0 -18 = 1.88888888889
x" = -8 + √676 2*-9 = -8 + 26.0 -18 = 18.0 -18 = -1.0
x' = 153.0
x" = -81.0
S = {x ∈ R / x' = 153.0, x" = -81.0 }