-4x2 +19x -15 = 0
ax2 bx c = 0
a = -4
b = 19
c = -15
Δ = b2-4ac
Δ = 19² - (4 * -4 * -15)
Δ = 361 - (4*60)
Δ = 361 - (240)
Δ = 121 Δ > 0
-4x2+19x-15=0
x = -b ∓ √Δ 2a
x' = -19 - √121 2*-4 = -19 - 11.0 -8 = -30.0 -8 = 3.75
x" = -19 + √121 2*-4 = -19 + 11.0 -8 = -8.0 -8 = 1.0
x' = 60.0
x" = 16.0
S = {x ∈ R / x' = 60.0, x" = 16.0 }