-12x2 -20x -7 = 0
ax2 bx c = 0
a = -12
b = -20
c = -7
Δ = b2-4ac
Δ = -20² - (4 * -12 * -7)
Δ = 400 - (4*84)
Δ = 400 - (336)
Δ = 64 Δ > 0
-12x2-20x-7=0
x = -b ∓ √Δ 2a
x' = 20 - √64 2*-12 = 20 - 8.0 -24 = 12.0 -24 = -0.5
x" = 20 + √64 2*-12 = 20 + 8.0 -24 = 28.0 -24 = -1.16666666667
x' = -72.0
x" = -168.0
S = {x ∈ R / x' = -72.0, x" = -168.0 }