-15x2 -20x +20 = 0
ax2 bx c = 0
a = -15
b = -20
c = 20
Δ = b2-4ac
Δ = -20² - (4 * -15 * 20)
Δ = 400 - (4*-300)
Δ = 400 - (-1200)
Δ = 1600 Δ > 0
-15x2-20x+20=0
x = -b ∓ √Δ 2a
x' = 20 - √1600 2*-15 = 20 - 40.0 -30 = -20.0 -30 = 0.666666666667
x" = 20 + √1600 2*-15 = 20 + 40.0 -30 = 60.0 -30 = -2.0
x' = 150.0
x" = -450.0
S = {x ∈ R / x' = 150.0, x" = -450.0 }