x-1/x=3 (x-1/x)2=x2-2+1/x2=9 x2+1/x2=11 (x+1/x)2=11+2=13 x4-1/x4=(x2+1/x2)(x2-1/x2)=11(x+1/x)(x-1/x)=33(x+1/x)=±33根号13