-9x2 -16x -7 = 0
ax2 bx c = 0
a = -9
b = -16
c = -7
Δ = b2-4ac
Δ = -16² - (4 * -9 * -7)
Δ = 256 - (4*63)
Δ = 256 - (252)
Δ = 4 Δ > 0
-9x2-16x-7=0
x = -b ∓ √Δ 2a
x' = 16 - √4 2*-9 = 16 - 2.0 -18 = 14.0 -18 = -0.777777777778
x" = 16 + √4 2*-9 = 16 + 2.0 -18 = 18.0 -18 = -1.0
x' = -63.0
x" = -81.0
S = {x ∈ R / x' = -63.0, x" = -81.0 }