-6x2 +19x +20 = 0
ax2 bx c = 0
a = -6
b = 19
c = 20
Δ = b2-4ac
Δ = 19² - (4 * -6 * 20)
Δ = 361 - (4*-120)
Δ = 361 - (-480)
Δ = 841 Δ > 0
-6x2+19x+20=0
x = -b ∓ √Δ 2a
x' = -19 - √841 2*-6 = -19 - 29.0 -12 = -48.0 -12 = 4.0
x" = -19 + √841 2*-6 = -19 + 29.0 -12 = 10.0 -12 = -0.833333333333
x' = 144.0
x" = -30.0
S = {x ∈ R / x' = 144.0, x" = -30.0 }