2/3-5/510/7-17/926/11-37/13设为(-1)^(n+1)*an/bn则bn=2n+1a2-a1=3=2*1+1a3-a2=5=2*2+1a4-a3=7=2*3+1……an-a(n-1)=2(n-1)+1相加an-a1=2*(1+2+……+n-1)+1*n=n^2a1=2an=n^2+2所以是(-1)^(n+1)*(n^2+2)/(2n+1)...