-4x2 -4x +15 = 0
ax2 bx c = 0
a = -4
b = -4
c = 15
Δ = b2-4ac
Δ = -4² - (4 * -4 * 15)
Δ = 16 - (4*-60)
Δ = 16 - (-240)
Δ = 256 Δ > 0
-4x2-4x+15=0
x = -b ∓ √Δ 2a
x' = 4 - √256 2*-4 = 4 - 16.0 -8 = -12.0 -8 = 1.5
x" = 4 + √256 2*-4 = 4 + 16.0 -8 = 20.0 -8 = -2.5
x' = 24.0
x" = -40.0
S = {x ∈ R / x' = 24.0, x" = -40.0 }