显然a≠0,a²-3a+1=0a²+1=3a两边平方a^4+2a²+1=9a²a^4+1=7a²两边除以a²a²+1/a²=7①a²+1/a²=7②a³-1/a³=(a - 1/a)(a²+1+1/a²)由a²-3a-1=0可得a-3-1/a=0,a-1/a=3所以②=3×8=24③a³+1/a³=(a+1/a)(a²-1+1/a²)a-1/a=3,(a-1/a)²=9,(a-1/a)²+4=13,a²+1/a²+2=13,a+1/a=±√13所以③=±6√13