-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 = -38.0 -8 = 4.75
x" = -15 + √529 2*-4 = -15 + 23.0 -8 = 8.0 -8 = -1.0
x' = 76.0
x" = -16.0
S = {x ∈ R / x' = 76.0, x" = -16.0 }