等差數(shù)列練習(xí)題求解答~
1.等差數(shù)列{an }中,a4=5 a9=15,求a14=_____
2.數(shù)列an=pn+q,p,q為常數(shù),an為等差數(shù)列,公差______
3.等差數(shù)列an中,a1=-5,a4=-½ 每相鄰兩項(xiàng)之間插入一個(gè)數(shù),使之仍為等差數(shù)列,則新等差數(shù)列通項(xiàng)公式為_(kāi)_____
4.{an}是公差為整數(shù)的等差數(shù)列,a1+a2+a3=15,a1a2a3=80,則a11+a12+a13=______
5.{an}等差數(shù)列,a1+a9=16.a4=1,則a12=_____
6.等差數(shù)列1,-1,-3,-5.-89.試問(wèn)該數(shù)列共有多少項(xiàng),
A92 B47 C46 D45
7.在等差數(shù)列an中,已知a1=1,a2+a4=10,an=39,則n=___
A.19 B.20 C.21 D.22
8.已知an為等差數(shù)列,a7-2a4=-1,a3=0,則公差d=
A.-2 B.-½ C.½ D.2