【模拟演练】
1.(2012·南京模拟)已知等差数列{an}满足a2+a4=4,a3+a5=10,则它的前10项的和S10=________.
2.(2012·无锡模拟)设等差数列{an}的前n项和为Sn,若1≤a5≤4,2≤a6≤3,则S6的取值范围是_______.
3.(2012·徐州模拟)等差数列{an},{bn}的前n项和分别为Sn,Tn,若 则 _______.
4.(2012·连云港模拟)设等差数列{an}的前n项和Sn,若S4=8,S8=20,则a11+a12+a13+a14=_______.
5.(2012·苏州模拟)已知数列{an},{bn}满足a1=1,a2=2,b1=2,且对任意的正整数i,j,k,l,当i+j=k+l时,都有ai+bj=ak+bl,则 的值是________.