把(2n+1)an=(2n-3)a(n-1)变形an/a(n-1)=(2n-3)/(2n+1)则a2/a1=1/5,a3/a2=3/7,a4/a3=5/9.a(n-1)/a(n-2)=(2n-5)/(2n-1),an/a(n-1)=(2n-3)/(2n+1)把各项依次相乘,得到3/(2n-1)(2n+1)=an/a1=an所以an=3/(2n-1)(2n+1)=(3/...