等差数列练习题求解答~

题目

等差数列练习题求解答~
1.等差数列{an }中,a4=5 a9=15,求a14=_____
2.数列an=pn+q,p,q为常数,an为等差数列,公差______
3.等差数列an中,a1=-5,a4=-½ 每相邻两项之间插入一个数,使之仍为等差数列,则新等差数列通项公式为______
4.{an}是公差为整数的等差数列,a1+a2+a3=15,a1a2a3=80,则a11+a12+a13=______
5.{an}等差数列,a1+a9=16.a4=1,则a12=_____
6.等差数列1,-1,-3,-5.-89.试问该数列共有多少项,
A92 B47 C46 D45
7.在等差数列an中,已知a1=1,a2+a4=10,an=39,则n=___
A.19 B.20 C.21 D.22
8.已知an为等差数列,a7-2a4=-1,a3=0,则公差d=
A.-2 B.-½ C.½ D.2

答案