-4x2 -15x +19 = 0
ax2 bx c = 0
a = -4
b = -15
c = 19
Δ = b2-4ac
Δ = -15² - (4 * -4 * 19)
Δ = 225 - (4*-76)
Δ = 225 - (-304)
Δ = 529 Δ > 0
-4x2-15x+19=0
x = -b ∓ √Δ 2a
x' = 15 - √529 2*-4 = 15 - 23.0 -8 = -8.0 -8 = 1.0
x" = 15 + √529 2*-4 = 15 + 23.0 -8 = 38.0 -8 = -4.75
x' = 16.0
x" = -76.0
S = {x ∈ R / x' = 16.0, x" = -76.0 }