亲爱的楼主:
a+1/a=3
a^2+1/a^2
=(a+1/a)^2-2=9-2=7
a^4+1/a^4
=(a^2+1/a^2)2-2
=[(a+1/a)2-2]^2-2
=49-2=47
祝您步步高升