x+1/x=6
(x²+1)/x=6
x²+1=6x
x²-6x+1=0
Δ=36-4=32
x1=(6-4√2)/2=2(3-2√2)/2=3-2√2
x2=3+2√2
S={3-2√2, 3+2√2)
daca x=3-2√2
x-1/x=3-2√2-1/(3-2√2)=3-2√2-(3+2√2)/(9-8)=
=3-2√2-3-2√2=-4√2
daca x=3+2√2
x-1/x=3+2√2-1/(3+2√2)=3+2√2-(3-2√2)/9-8)=
=3+2√2-3+2√2=4√2
