a²-a-1=0a²/a-a/a-1/a=0a-1/a=1(a-1/a)²=a²+1/a²-2=1a²+1/a²=3(a²+1/a²）²=a^4+1/a^4+2=9a^4+1/a^4=7 所以a四次方+a四次方分之一=7