-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 = 49 Δ > 0
-4x2+17x-15=0
x = -b ∓ √Δ 2a
x' = -17 - √49 2*-4 = -17 - 7.0 -8 = -24.0 -8 = 3.0
x" = -17 + √49 2*-4 = -17 + 7.0 -8 = -10.0 -8 = 1.25
x' = 48.0
x" = 20.0
S = {x ∈ R / x' = 48.0, x" = 20.0 }