由m+1/m=3，两边平方，得m²+1/m²+2=9，所以m²+1/m²=7m²-1/m²=(m+1/m)(m-1/m)=3(m-1/m)|m-1/m|=√(m-1/m)²=√[(m+1/m)²-4]=√5所以，当m-1/m≥0时，m²-1/m² =3(m-1/m)=3√5当m-1/m<0时，m²-1/m² =3(m-1/m)=-3√5
m²+1/m²=(m+1/m)^2-2m*1/m=3^2-2=7
