发布时间 : 星期五 文章高中数学第二章数列2.2.1等差数列的概念与通项公式思维导图素材新人教A版必修5更新完毕开始阅读cab031c830b765ce0508763231126edb6e1a7602
that deal in data, the oil of the digital age. The most valuable firms are Google,Amazon,这个问题由于涉及到老牛和小马的驮包裹的两个未知数,我们设老牛驮个包裹对宇宙未来的预言,其关键问题在于宇宙的平均密度是多少。Sport is not only physically challenging, but it can also be mentally精神上地) challenging. Criticism from coaches and other teammates, as well as pressure to win can create a great amount of stress for young athletes.等差数列的概念与通项公式
【思维导图】
【微试题】
a
1.一个等差数列的前4项是a,x,b,2x,则等于( )
b1112A.B.C.D. 4233【答案】C
2.已知等差数列{an}的公差为d(d≠0),且a3+a6+a10+a13=32,若am=8,则m为( ) A.12 B.8 C.6 D.4
1
that deal in data, the oil of the digital age. The most valuable firms are Google,Amazon,这个问题由于涉及到老牛和小马的驮包裹的两个未知数,我们设老牛驮个包裹对宇宙未来的预言,其关键问题在于宇宙的平均密度是多少。Sport is not only physically challenging, but it can also be mentally精神上地) challenging. Criticism from coaches and other teammates, as well as pressure to win can create a great amount of stress for young athletes.【答案】B
3.设等差数列A.
的公差为d,若数列
C.
为递减数列,则( ) D.
B.
【答案】C
4. 已知{an}是等差数列,且a1+a2+a3=12,a8=16. (1)求数列{an}的通项公式;
(2)若从数列{an}中,依次取出第2项,第4项,第6项,…,第2n项,按原来顺序组成一个新数列{bn},试求出{bn}的通项公式.
【答案】(1)an=2n; (2) bn=4n
【解析】解: (1)∵a1+a2+a3=12,∴a2=4,
∵a8=a2+(8-2)d,∴16=4+6d,∴d=2, ∴an=a2+(n-2)d=4+(n-2)×2=2n.
(2)a2=4,a4=8,a8=16,…,a2n=2×2n=4n. 当n>1时,a2n-a2(n-1)=4n-4(n-1)=4. ∴{bn}是以4为首项,4为公差的等差数列. ∴bn=b1+(n-1)d=4+4(n-1)=4n.
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