-15x2 +19x -4 = 0
ax2 bx c = 0
a = -15
b = 19
c = -4
Δ = b2-4ac
Δ = 19² - (4 * -15 * -4)
Δ = 361 - (4*60)
Δ = 361 - (240)
Δ = 121 Δ > 0
-15x2+19x-4=0
x = -b ∓ √Δ 2a
x' = -19 - √121 2*-15 = -19 - 11.0 -30 = -30.0 -30 = 1.0
x" = -19 + √121 2*-15 = -19 + 11.0 -30 = -8.0 -30 = 0.266666666667
x' = 225.0
x" = 60.0
S = {x ∈ R / x' = 225.0, x" = 60.0 }