∵[a^(1/2)-a^(-1/2)]² =a+1/a-2 =3-2 =1∴ a^(1/2)-a^(-1/2)=1或-1a^(3/2)-a^(-2/3) =[a^(1/2)-a^(-1/2)][a+1/a-a^(1/2)·a^(-1/2)] =±1·[3-1] =±2
