-4x2 -15x +4 = 0
ax2 bx c = 0
a = -4
b = -15
c = 4
Δ = b2-4ac
Δ = -15² - (4 * -4 * 4)
Δ = 225 - (4*-16)
Δ = 225 - (-64)
Δ = 289 Δ > 0
-4x2-15x+4=0
x = -b ∓ √Δ 2a
x' = 15 - √289 2*-4 = 15 - 17.0 -8 = -2.0 -8 = 0.25
x" = 15 + √289 2*-4 = 15 + 17.0 -8 = 32.0 -8 = -4.0
x' = 4.0
x" = -64.0
S = {x ∈ R / x' = 4.0, x" = -64.0 }