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µÃ:f+f=4(x¡ÊR),ËùÒÔº¯Êýf(x)¹ØÓÚµã¶Ô³Æ,Áît=-x,Ôò+x=1-t,
µÃµ½f(t)+f(1-t)=4.ÒòΪan=f(0)+f+¡+f+f(1),ÓÖÒòΪan=f(1)+f+¡
+f+f(0),µ¹ÐòÏà¼Ó¿ÉµÃ2an=4(n+1),¼´an=2(n+1).
11.ÒÑÖªº¯Êýf(x)=)= ( )
(x¡ÊR),ÈôµÈ±ÈÊýÁÐ{an}Âú×ãa1a2 019=1,Ôòf(a1)+f(a2)+f(a3)+¡+f(a2
019
A.2 019 B. C.2 D.
¡¾½âÎö¡¿Ñ¡A.ÒòΪa1a2 019=1,
ËùÒÔf(a1)+f(a2 019)=+=+=+=2.
ÒòΪ{an}ΪµÈ±ÈÊýÁÐ,Ôò
a1a2 019=a2a2 018=¡=a1 009a1 011==1,
ËùÒÔf(a2)+f(a2 018)=2,¡,f(a1 009)+f(a1 011)=2,f(a1 010)=1. ¼´f(a1)+f(a2)+f(a3)+¡+f(a2 019) =2¡Á1 009+1=2 019.
12.ÈôÕýÏîµÝÔöµÈ±ÈÊýÁÐ{an}Âú×ã1+(a2-a4)+¦Ë(a3-a5)=0(¦Ë¡ÊR),Ôòa6+¦Ëa7µÄ×îСֵΪ ÊÀ¼Í½ð°ñµ¼Ñ§ºÅ( ) A.-2
B.-4
C.2 D.4
¡¾½âÎö¡¿Ñ¡D.ÒòΪ{an}ÊÇÕýÏîµÝÔöµÄµÈ±ÈÊýÁÐ,
ËùÒÔa1>0,q>1,ÓÉ1+(a2-a4)+¦Ë(a3-a5)=0,µÃ1+(a2-a4)+¦Ëq(a2-a4)=0, ËùÒÔ1+¦Ëq=
,
ËùÒÔa6+¦Ëa7=a6(1+¦Ëq)==
==(q-1)+2+
2
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2+2=4(q-1>0),
2
µ±ÇÒ½öµ±q=ʱȡµÈºÅ,ËùÒÔa6+¦Ëa7µÄ×îСֵΪ4.
¶þ¡¢Ìî¿ÕÌâ(±¾´óÌâ¹²4СÌâ,ÿСÌâ5·Ö,¹²20·Ö.Çë°ÑÕýÈ·´ð°¸ÌîÔÚÌâÖкáÏßÉÏ) 13.(2020¡¤Ì©°²Ä£Äâ)ÒÑÖªÊýÁÐ{an}ΪµÈ²îÊýÁÐÇÒa7=,Ôòsin(a2+a12)= .
¡¾½âÎö¡¿ÔڵȲîÊýÁÐ{an}ÖÐ,ÓÉa7=,µÃa2+a12=2a7=.
ËùÒÔsin(a2+a12)=sin=.
´ð°¸:
¡¾±äʽ±¸Ñ¡¡¿
ÉèµÈ±ÈÊýÁÐ{an}µÄ¹«±Èq=2,Ç°n ÏîºÍΪSn,Ôò
= .
¡¾½âÎö¡¿====.
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14.ÈôÈýÊý³ÉµÈ±ÈÊýÁÐ,Æä»ýΪ8,Ê×Ä©Á½ÊýÖ®ºÍΪ4,Ôò¹«±ÈqµÄֵΪ .
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Çó³ö´ð°¸:1
¹«±ÈqµÄֵΪ1.
15.(2020¡¤ºªµ¦Ä£Äâ)ÒÑÖªÊýÁÐ{an},{bn}µÄÇ°nÏîºÍ·Ö±ðΪSn,Tn,bn-an=2+1,ÇÒSn+Tn=2+n-2,Ôò2Tn= .
¡¾½âÎö¡¿ÓÉÌâÒâÖªTn-Sn=b1-a1+b2-a2+¡+bn-an=n+2-2,ÓÖSn+Tn=2+n-2,ËùÒÔ2Tn=Tn-Sn+Sn+Tn=2+n(n+1)-4. ´ð°¸:2+n(n+1)-4
16.(2020¡¤ÉòÑôÄ£Äâ)¸÷Ïî¾ùΪÕýżÊýµÄÊýÁÐa1,a2,a3,a4ÖÐ,Ç°ÈýÏîÒÀ´Î³É¹«²îΪd(d>0)µÄµÈ²îÊýÁÐ,ºóÈýÏîÒÀ´Î³É¹«±ÈΪqµÄµÈ±ÈÊýÁÐ.Èôa4-a1=88,ÔòqµÄËùÓпÉÄܵÄÖµ¹¹³ÉµÄ¼¯ºÏΪ .
ÊÀ¼Í½ð°ñµ¼Ñ§ºÅ n+2
n+2
n+1
n+1
2
nn+12
¡¾½âÎö¡¿ÒòΪǰÈýÏîÒÀ´Î³É¹«²îΪd(d>0)µÄµÈ²îÊýÁÐ,a4-a1=88,ËùÒÔÕâËÄÏî¿ÉÒÔÉèΪa1,a1+d,a1+2d,a1+88,ÆäÖÐa1,dΪÕýżÊý,ºóÈýÏîÒÀ´Î³É¹«±ÈΪqµÄµÈ±ÈÊýÁÐ,ËùÒÔÓÐ
=,ÕûÀíµÃa1=>0,µÃ
(d-22)(3d-88)<0,22 µ±d=24ʱ,a1=12,q=;µ±d=26ʱ,a1=,²»·ûºÏÌâÒâ,ÉáÈ¥;µ±d=28ʱ,a1=168,q=,¹ÊqµÄ ËùÓпÉÄܵÄÖµ¹¹³ÉµÄ¼¯ºÏΪ. ´ð°¸: Èý¡¢½â´ðÌâ(±¾´óÌâ¹²6СÌâ,¹²70·Ö.½â´ðʱӦд³ö±ØÒªµÄÎÄ×Ö˵Ã÷¡¢Ö¤Ã÷¹ý³Ì»òÑÝËã²½Öè) 17.(10·Ö)ÒÑÖªµÈ²îÊýÁÐ{an}µÄ¹«²îd²»Îª0,a1=3,ÇÒa2,a4,a7³ÉµÈ±ÈÊýÁÐ. (1)Çó{an}µÄͨÏʽ. (2)Çóa2+a4+a6+¡+a2n. ¡¾½âÎö¡¿(1)ÒòΪa2,a4,a7³ÉµÈ±ÈÊýÁÐ,ËùÒÔ¼´(a1+3d)=(a1+d)(a1+6d),»¯¼òµÃ (a1-3d)d=0, ÒòΪ¹«²îd¡Ù0,ËùÒÔa1=3d, ÒòΪa1=3,ËùÒÔd=1,ËùÒÔan=a1+(n-1)d=n+2. 2 =a2a7, (2)ÓÉ(1)Öªa2n=2n+2,¹Ê{a2n}ÊÇÊ×ÏîΪ4¡¢¹«²îΪ2µÄµÈ²îÊýÁÐ, ËùÒÔa2+a4+a6+¡+a2n=¡¾±äʽ±¸Ñ¡¡¿ ==n+3n. 2 ÒÑÖªµÈ±ÈÊýÁÐ{an}µÄÇ°nÏîºÍΪSn,Âú×ãS4=2a4-1,S3=2a3-1. (1)Çó{an}µÄͨÏʽ. (2)¼Çbn=lo ,Çób1+b2+¡+bnµÄ×î´óÖµ. ¡¾½âÎö¡¿(1)Éè{an}µÄ¹«±ÈΪq,ÓÉS4-S3=a4,µÃ2a4-2a3=a4,ËùÒÔÓÖÒòΪS3=2a3-1,ËùÒÔa1+2a1+4a1=8a1-1,ËùÒÔa1=1.ËùÒÔan=2. n n-1 =2,ËùÒÔq=2. (2)ÓÉ(1)Öª,Sn==2-1, ËùÒÔbn=lo=2log22=8-2n,bn+1-bn=-2,b1=8-2=6, 4-n ËùÒÔÊýÁÐ{bn}ÊÇÊ×ÏîΪ6,¹«²îΪ-2µÄµÈ²îÊýÁÐ,ËùÒÔb2=4,b3=2,b4=0,µ±n¡Ý5ʱbn<0,ËùÒÔµ±n=3»òn=4ʱ,b1+b2+¡+bnµÄ×î´óֵΪ12. 18.(12·Ö)(2020¡¤³¤É³Ä£Äâ)ÉèSnÊÇÊýÁÐ{an}µÄÇ°nÏîºÍ,ÒÑÖªa1=1,Sn=2-2an+1. (1)ÇóÊýÁÐ{an}µÄͨÏʽ. (2)Éèbn=(-1)lo n an,ÇóÊýÁÐ{bn}µÄÇ°nÏîºÍTn. ¡¾½âÎö¡¿(1)ÒòΪSn=2-2an+1,a1=1,