-4x2 +21x -17 = 0
ax2 bx c = 0
a = -4
b = 21
c = -17
Δ = b2-4ac
Δ = 21² - (4 * -4 * -17)
Δ = 441 - (4*68)
Δ = 441 - (272)
Δ = 169 Δ > 0
-4x2+21x-17=0
x = -b ∓ √Δ 2a
x' = -21 - √169 2*-4 = -21 - 13.0 -8 = -34.0 -8 = 4.25
x" = -21 + √169 2*-4 = -21 + 13.0 -8 = -8.0 -8 = 1.0
x' = 68.0
x" = 16.0
S = {x ∈ R / x' = 68.0, x" = 16.0 }