m^2-5m-1=0m≠0,两边同除以m,得m-1/m=5(m-1/m)²=25m²+1/m²-2=25m²+1/m²=27m^2-5m=12m^2-5m+（1/m^2）=m²+m²-2m+(1/m²)=m²+(1/m²)+1=27+1=28m²+1/m²-2=25m²+1/m²=2323应该改为27吧！