Х²+1/х²=(х-1/х)²+2
3(х-1/х)+2*[(х-1/х)²+2]-4=0
х-1/х=а
3а+2a²+4-4=0
3a+2a²=0
a(3+2a)=0
a=0⇒x-1/x=0⇒x²-1=0⇒x²=1⇒x=-1 U x=1
2a+3=0⇒2a=-3⇒a=-3/2⇒x-1/x=-3/2⇒2x²+3a-2=0
D=9+16=25
x3=(-3-5)/4=-2 U x4=(-3+5)/4=1/2
(x1+x2+x3+x4)/4=(-1+1-2+0,5)/4=-1,5/4=-0,375