a²-5a+1=0则a²+1=5a
则a+1/a=5
a²除以a4次方+a²+1
=1÷(a²+1+1/a²)
=1÷(a²+2+1/a²-1)
=1÷[(a+1/a)²-1]
=1÷(25-1)
=1/24