-4x2 +17x +15 = 0
ax2 bx c = 0
a = -4
b = 17
c = 15
Δ = b2-4ac
Δ = 17² - (4 * -4 * 15)
Δ = 289 - (4*-60)
Δ = 289 - (-240)
Δ = 529 Δ > 0
-4x2+17x+15=0
x = -b ∓ √Δ 2a
x' = -17 - √529 2*-4 = -17 - 23.0 -8 = -40.0 -8 = 5.0
x" = -17 + √529 2*-4 = -17 + 23.0 -8 = 6.0 -8 = -0.75
x' = 80.0
x" = -12.0
S = {x ∈ R / x' = 80.0, x" = -12.0 }